20 RIDDLES TO TEST YOUR MATH, IQ AND THINKING SKILLS.

[ash9898]

1. What is the value of x If 1/2, 2/3, 3/4, 4/5, 5/6, 6/7, 7/8, 8/9, 9/10 then x/1000?

2. If 4 and 2= 26, 8 and 1 = 79 and 6 and 5 = 111. Then, what is 7and3?

3. What 3 positive numbers give the same result when multiplied and added together?

4. What number do you get when you multiply all of the numbers on a telephone's number pad?

5. Here is a light switch. Note the order of the positions. If the light is now at medium and it is switched 3922 times what will be the position of the switch?

6. Can you arrange four nines to make it equal to 100.

8. If 1/2 of 5 is 3, then what is 1/3 of 10?

9. 100 students entered college. 55 of them chose music. 44 of them chose sports. 20 of them chose both. How many of them chose neither music nor sports?

10. Four friends are going to a concert. When they arrive, there are only five seats together left in the theater. The manager will let all four friends in for free if one of them can tell her how many different seating arrangements are possible for four people with five empty seats.

All four are let in free. Could you have given the correct answer?

12. At six o’clock the wall clock struck 6 times. Checking with my watch, I noticed that the time between the first and last strokes was 30 seconds. How long will the clock take to strike 12 at midnight?

13. There are several books on a bookshelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

14. John has been hired to paint the numbers 1 through 100 on 100 apartments.

How many times he has to paint 8?

15. You have two books. One of them is upside-down and the other is rotated so the top of the book is facing you.

What is the sum of the first page in each book?

16. There is a certain club which is for men only. There are 600 men who belong to this club and 5% of these men wear one earring. Of the other 95% membership, half wear two earrings and the other half wear none. How many earrings are being worn in this club?

17. Does a pound of gold or a pound of feathers weight more?

18. There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?

19.Little Johnny is walking home. He has $300 he has to bring home to his mom. While he is walking a man stops him and gives him a chance to double his money. The man says "I'll give you $600 if you can roll 1 die and get a 4 or above, you can roll 2 dice and get a 5 or 6 on at least one of them, or you can roll 3 dice and get a 6 on at least on die. If you don't I get your $300."

What does Johnny do to have the best chance of getting home with the money?

20. If you have 6 women and 2 friends, how many women do each of your friends get?

I created this video 20 RIDDLES TO TEST YOUR MATH, IQ AND THINKING SKILLS.  And I wanted to share it with you, Try to answer all riddles, And let me know your feedback. Thanks, and Good Luck!

[DejMar]

  Reveal hidden contents

 

1. Dependant upon what is intended by the ambiguously written question, the value of  x could be either 999, where each rational number is computed as n/(n+1) with (n+1) is given to be 1000, or x could be 10000/11 if the fractions are given in a sequence of terms with each nth term having the value n/(n+1).

2. Given each equation as a and b = c, c is (a - b)||(a + b), and it follows that 7 and 3 = 410.
(Note: || is a standard symbol of concatenation)

3. For a*b*c = (a+b+c) the three numbers are {1, 2, 3}.
(1*2*3) = (1+2+3) = 6.

4. As one of the numbers is 0, the product of those numbers is 0.

5. There is evidence that the problem is not fully transcribed and presented here.

6. 99 + 9/9 = 100

7. The riddle is "why is there no problem enumerated as 7?"

8. If the product is rounded to the nearest whole number, upwards where it is a fraction and equally distant to the two whole numbers it is nearest, then 1/3 of 10 = 3. If the product is always rounded upward to the nearest whole number, then then 1/3 of 10 = 4.

9. 80. [55 - 20] + (100 - 55) = 80 and [44 - 20] + (100 - 44) = 80.

10. Yes. 5! = 125.

12. Assuming that each strike is given at a constant rate, it should take the 1 minute (i.e, 60 seconds) for the clock to strike 12 times to represent the midnight hour. The final stroke of 6 o'clock being at 6:00:30 and the final stroke of midnight being at 00:01:00.

13. 9.

14. There are nineteen 8's represented in the numbers between 1 and 100.

15. Books do not always follow the same numbering system. Given the assumption that the first page of a book is assigned as 1, and using the definition of sum requiring two or more addends, the sum of these two page numbers is 2. The orientation of the book does not change the page number.

16. 600 earrings.

17. Depends upon the units of weight and systems being used. A pound of gold is generally given in troy units and a pound of feathers is generally given in the avoirdupois system. If the units of measure are in the same system, the are of equal weight. If the units correspond to their respective standards, then a avoirdupois pound of feathers weighs more than the troy pound of gold.

18. As the center of the chain is at half the length of the chain, which is also the distance in which the chain dips, the two ends nailed to the wall would be nailed at the same place. The two ends would be zero feet from each other.

19. Little Johnny has a 50% chance of winning with rolling one standard die. His odds are increased to approximately 55.56% with rolling two standard dice. His odds are decreased to approximately 42.13% with rolling three standard dice. The best odds of getting home with any money (100%) is if Little Johnny does not play. If the question is the odds of getting home with "the money", with "the money" being the total of $600, Little Johnny would best gamble using two dice.

20. The problem is not clearly stated. Are the women being transferred as if they are property? Is there a possibility of sharing the number of women gotten or is there a distinct division?     

 

 

Edited June 18, 2018 by DejMar
typeface changes

[rocdocmac]

My answers

 

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1. 999

2. 410

3. 1,2,3

4. zero

5. high

6. 99/99 or 99/.99

7. no riddle!

8. 4 (rounding up to the nearest integer = ceiling; any number from 2.000000... to exactly 2.5000000... will round to 2,  not 3)

9. 31

10. 120 (permutation 5P4)

11.  no riddle!

12. 66 sec.

13. 9

14. 20

15. 2 pages

16. 600

17. Masses are the same. Weights differ ... the gold is heavier since it loses less weight in air because of its smaller volume (Archimedes' principle is also applicable to gasses). The weights will only be the same in vacuum.

18. zero feet

19. Johnny shouldn't take the bet (!00 % chance  of bringing all $300 back home)

20. I  have all 6 women, my  friends get none.

 

 

  On 6/18/2018 at 11:37 AM, rocdocmac said:

5. high

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Changing my answer to the OFF position.

 

Edited June 18, 2018 by rocdocmac
typo

[plasmid]

I watched the video, and overall liked it. Since you asked for feedback: with the video format, I think I would prefer to see the question and be told to pause to have time to think of the answer before it appears instead of having a set amount of time for each question, since with at least some of them you either know it or you don't right off the bat. As it is, I got a little annoyed waiting a minute for the answer if I already knew it.

The other main comment is something DejMar sort of alluded to, that there are potentially multiple answers that would make sense for some of the riddles. In particular the second one, I also interpreted it as most likely being a gotcha where each number in the sequence is (n)/(n+1), so the final term x/1000 comes after 9/10 and should equal 10/11, meaning x = 10 x 1000 / 11. Only after realizing that it wouldn't be an integer did I decide that it probably wasn't what you intended to ask, so the answer should be the other thing I had in mind and be x = 999. With the light switch, when I saw it here I thought there must be three positions with something like "off" going to "medium", "medium" going either to "off" or to "high", and "high" going only to "medium" so there would be a unique answer -- after any even number of flips the switch must be back at "medium" -- whereas with the youtube version if you change directions during flipping you could either end up at the original position or 180 degrees away. For the question of painting 8s, I could have interpreted a couple of ways: you could argue that he would only paint 8 once (if it's referring to house number 8, or just the number 8 and not other numbers that happen to have 8 as a digit), that he would paint it 20 times (if you mean the total number of digits that are 8), or maybe even 19 times (if you mean the total number of houses with any 8 on them, although that's a less likely interpretation). DejMar commented on the ambiguity of whether the question with Little Johnny is talking about making it home with the original $300 dollars or the money that the man is offering, but I suppose that ambiguity needs to be present or else it wouldn't be much of a riddle. And the last question seems like it might be a bit offensive if asked to a woman.

It might not be possible to make the questions entirely unambiguous, especially the question about Little Johnny since the ambiguity is what makes it a riddle in the first place, but sometimes simple things like saying "how many times does he have to paint the digit 8" can help make it unambiguous. In general, I would say to check for (and ask other people to check for) unintended ways that the questions might be interpreted.

[ash9898]

  On 6/18/2018 at 2:18 PM, plasmid said:

I watched the video, and overall liked it. Since you asked for feedback: with the video format, I think I would prefer to see the question and be told to pause to have time to think of the answer before it appears instead of having a set amount of time for each question, since with at least some of them you either know it or you don't right off the bat. As it is, I got a little annoyed waiting a minute for the answer if I already knew it.

Expand  

Thank you so much, I really appreciate that you point out this, I will fix this in my next video. 

And overall I agree with most of your opinions and I will do my best. 

Update.

5. Image attached with this reply.

7. Divide 110 into two parts so that one will be 150 percent of the other. What are the 2 numbers?

11. The number of bacteria in a large sealed jar doubles every minute. The bacteria will take an hour to fill the jar. When will the jar be half full?

20. I added just for fun!

 

And Honestly, I apologize for the errors I made in this thread, Sorry for ruining your fun and Thank you all for being so nice. This is a great forum. I love you all.

 

[rocdocmac]

Didn't watch the video - Will take too much data (for me)! Please show us the answers after everyone has had a go at them!

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7. 44 and 56

11.  After 59 minutes

 

[Donald Cartmill]

. What is the value of x If 1/2, 2/3, 3/4, 4/5, 5/6, 6/7, 7/8, 8/9, 9/10 then x/1000?  x = 500,000

2. If 4 and 2= 26, 8 and 1 = 79 and 6 and 5 = 111. Then, what is 7and3?...410

3. What 3 positive numbers give the same result when multiplied and added together?  2

4. What number do you get when you multiply all of the numbers on a telephone's number pad?  zero

5. Here is a light switch. Note the order of the positions. If the light is now at medium and it is switched 3922 times what will be the position of the switch?  medium

6. Can you arrange four nines to make it equal to 100.    99 9/9

8. If 1/2 of 5 is 3, then what is 1/3 of 10?  3.67

9. 100 students entered college. 55 of them chose music. 44 of them chose sports. 20 of them chose both. How many of them chose neither music nor sports?   21

10. Four friends are going to a concert. When they arrive, there are only five seats together left in the theater. The manager will let all four friends in for free if one of them can tell her how many different seating arrangements are possible for four people with five empty seats.     240

All four are let in free. Could you have given the correct answer?   240

12. At six o’clock the wall clock struck 6 times. Checking with my watch, I noticed that the time between the first and last strokes was 30 seconds. How long will the clock take to strike 12 at midnight?       5 hrs 59 1/2 minutes

13. There are several books on a bookshelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?   9

14. John has been hired to paint the numbers 1 through 100 on 100 apartments.   11

How many times he has to paint 8?   11

15. You have two books. One of them is upside-down and the other is rotated so the top of the book is facing you.

What is the sum of the first page in each book?    1 +1

16. There is a certain club which is for men only. There are 600 men who belong to this club and 5% of these men wear one earring. Of the other 95% membership, half wear two earrings and the other half wear none. How many earrings are being worn in this club?    600

17. Does a pound of gold or a pound of feathers weight more?  feathers

18. There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?            on the same nail

19.Little Johnny is walking home. He has $300 he has to bring home to his mom. While he is walking a man stops him and gives him a chance to double his money. The man says "I'll give you $600 if you can roll 1 die and get a 4 or above, you can roll 2 dice and get a 5 or 6 on at least one of them, or you can roll 3 dice and get a 6 on at least on die. If you don't I get your $300."

What does Johnny do to have the best chance of getting home with the money?  keep on walking

20. If you have 6 women and 2 friends, how many women do each of your friends get            if the friends are two of the 6 women;i.e. women themselves , then each is entitled to herself, or one each/   If the two friends are male then no women.

[Donald Cartmill]

. What is the value of x If 1/2, 2/3, 3/4, 4/5, 5/6, 6/7, 7/8, 8/9, 9/10 then x/1000?  x = 500,000

2. If 4 and 2= 26, 8 and 1 = 79 and 6 and 5 = 111. Then, what is 7and3?...410

3. What 3 positive numbers give the same result when multiplied and added together?  2 mis interpreted the Q 1,2,3 is correct

4. What number do you get when you multiply all of the numbers on a telephone's number pad?  zero

5. Here is a light switch. Note the order of the positions. If the light is now at medium and it is switched 3922 times what will be the position of the switch?  medium I assumed in the absence of additional info there were 3 positions  .  i.e low , med , high. any even number of flips will put the sw back on med

6. Can you arrange four nines to make it equal to 100.    99 9/9

8. If 1/2 of 5 is 3, then what is 1/3 of 10?  3.67    I envisioned 1/2 of 5 = 2 1/2 + 1/2 = 3;  therefore 1/3 of 10 = 3.33 + 1/3 =3.367

9. 100 students entered college. 55 of them chose music. 44 of them chose sports. 20 of them chose both. How many of them chose neither music nor sports?   21

10. Four friends are going to a concert. When they arrive, there are only five seats together left in the theater. The manager will let all four friends in for free if one of them can tell her how many different seating arrangements are possible for four people with five empty seats.     120  5 seats taken 4 at a time  5 !

All four are let in free. Could you have given the correct answer?   120    5 seats taken 4 at a time  5 !

12. At six o’clock the wall clock struck 6 times. Checking with my watch, I noticed that the time between the first and last strokes was 30 seconds. How long will the clock take to strike 12 at midnight?       5 hrs 59 1/2 minutes

13. There are several books on a bookshelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?   9

14. John has been hired to paint the numbers 1 through 100 on 100 apartments.   my bad 20

How many times he has to paint 8?   20

15. You have two books. One of them is upside-down and the other is rotated so the top of the book is facing you.

What is the sum of the first page in each book?    1 +1

16. There is a certain club which is for men only. There are 600 men who belong to this club and 5% of these men wear one earring. Of the other 95% membership, half wear two earrings and the other half wear none. How many earrings are being worn in this club?    600

17. Does a pound of gold or a pound of feathers weight more?  feathers

18. There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?            on the same nail

19.Little Johnny is walking home. He has $300 he has to bring home to his mom. While he is walking a man stops him and gives him a chance to double his money. The man says "I'll give you $600 if you can roll 1 die and get a 4 or above, you can roll 2 dice and get a 5 or 6 on at least one of them, or you can roll 3 dice and get a 6 on at least on die. If you don't I get your $300."

What does Johnny do to have the best chance of getting home with the money?  keep on walking

20. If you have 6 women and 2 friends, how many women do each of your friends get            if the friends are two of the 6 women;i.e. women themselves , then each is entitled to herself, or one each/   If the two friends are male then no women.

[rocdocmac]

  On 6/18/2018 at 11:37 AM, rocdocmac said:

9. 31

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Make that 21!

 

[Donald Cartmill]

. What is the value of x If 1/2, 2/3, 3/4, 4/5, 5/6, 6/7, 7/8, 8/9, 9/10 then x/1000?  x = 500,000  CORRECTION   x =900

2. If 4 and 2= 26, 8 and 1 = 79 and 6 and 5 = 111. Then, what is 7and3?...410

3. What 3 positive numbers give the same result when multiplied and added together?  2 mis interpreted the Q 1,2,3 is correct

4. What number do you get when you multiply all of the numbers on a telephone's number pad?  zero

5. Here is a light switch. Note the order of the positions. If the light is now at medium and it is switched 3922 times what will be the position of the switch?  medium I assumed in the absence of additional info there were 3 positions  .  i.e low , med , high. any even number of flips will put the sw back on med

6. Can you arrange four nines to make it equal to 100.    99 9/9

8. If 1/2 of 5 is 3, then what is 1/3 of 10?  3.67    I envisioned 1/2 of 5 = 2 1/2 + 1/2 = 3;  therefore 1/3 of 10 = 3.33 + 1/3 =3.367

9. 100 students entered college. 55 of them chose music. 44 of them chose sports. 20 of them chose both. How many of them chose neither music nor sports?   21

Of the 55 ,20 choose both leaving 35 ; of the 44 ,20 choose both leaving 24;             35 music only ;24 sports only ; 20 M&S  total=79  100 - 79 = 21 who do neither

10. Four friends are going to a concert. When they arrive, there are only five seats together left in the theater. The manager will let all four friends in for free if one of them can tell her how many different seating arrangements are possible for four people with five empty seats.     120  5 seats taken 4 at a time  5 !

All four are let in free. Could you have given the correct answer?   120    5 seats taken 4 at a time  5 !

12. At six o’clock the wall clock struck 6 times. Checking with my watch, I noticed that the time between the first and last strokes was 30 seconds. How long will the clock take to strike 12 at midnight?       5 hrs 59 1/2 minutes  NOTE: the question is not how long it chimes at 12 :00 ,but how long from the 30 seconds of chiming at 6:00

3. There are several books on a bookshelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?   9

14. John has been hired to paint the numbers 1 through 100 on 100 apartments.   my bad 20

How many times he has to paint 8?   20

15. You have two books. One of them is upside-down and the other is rotated so the top of the book is facing you.

What is the sum of the first page in each book?    1 +1   Up side down ,laying on its side ,propped at an angle the first page is 1 

16. There is a certain club which is for men only. There are 600 men who belong to this club and 5% of these men wear one earring. Of the other 95% membership, half wear two earrings and the other half wear none. How many earrings are being worn in this club?    600

17. Does a pound of gold or a pound of feathers weight more?  feathers      A pound of feathers weighs  16 ounces avoirdupois;  Gold is weighed on the troy system whereby a troy pound is 12 oz ;   1 troy oz  = 1.0971 oz avoirdupois  therefore 1 pound of gold weighs 13.1652 oz avoirdupois

18. There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?            on the same nail

19.Little Johnny is walking home. He has $300 he has to bring home to his mom. While he is walking a man stops him and gives him a chance to double his money. The man says "I'll give you $600 if you can roll 1 die and get a 4 or above, you can roll 2 dice and get a 5 or 6 on at least one of them, or you can roll 3 dice and get a 6 on at least on die. If you don't I get your $300."

What does Johnny do to have the best chance of getting home with the money?  keep on walking

20. If you have 6 women and 2 friends, how many women do each of your friends get            if the friends are two of the 6 women;i.e. women themselves , then each is entitled to herself, or one each/   If the two friends are male then no women.

[DejMar]

As problems #9 and #14, I admit to having made errors.
 

  Reveal hidden contents

The number of students choosing neither music nor sports for college would be 100 - ((55 - 20) + (44 - 20) + 20) = 21; and, the number of 8's to be painted would be 20.

Problem #12 is one of the problems that can have more than one correct answer. That is, there is more than one way of defining a stroke of a wall clock.

 

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A strike might be defined as the length of time from the  beginning of a chime to the beginning of the next chime, if one were to follow; and all chimes are of equal length. Under this definition, the six o'clock six strikes given to be 30 seconds would mean each strike was 5 seconds in length. The twelve strikes at midnight would be 60 seconds. Another definition of a strike may define it as the almost infinitesmal point of time where a chime begins. In this latter assumed definition, the problem assigns the 30 seconds from the first chime of the hour through each interval and subsequent chimes to the last chime of that hour. Basically, the length of time is but the measure of the intervals between each chime, and dismissing the interval of time between the hour's final chime to the beginning of the next hour's chime. With this definition, the 30 seconds would be divided by the five intervals and establish that the length of the standard interval would be 6 seconds long. The number of intervals during the midnight series of chimes would be eleven. 6 seconds X 11 intervals = 66 seconds for the length of the midnight's twelve strikes.

 

Edited June 21, 2018 by DejMar
removal of added white space

[Donald Cartmill]

OK I disagree with our most sage and top contributor rocdocmac  on 5, 8 ,  12 is ok if you add 30 seconds  ,17 ,20 .    In addition I will be making corrections to  #1

 

. What is the value of x If 1/2, 2/3, 3/4, 4/5, 5/6, 6/7, 7/8, 8/9, 9/10 then x/1000?  x = 500,000  CORRECTION 2 = 999

2. If 4 and 2= 26, 8 and 1 = 79 and 6 and 5 = 111. Then, what is 7and3?...410

3. What 3 positive numbers give the same result when multiplied and added together?  2 mis interpreted the Q 1,2,3 is correct

4. What number do you get when you multiply all of the numbers on a telephone's number pad?  zero

5. Here is a light switch. Note the order of the positions. If the light is now at medium and it is switched 3922 times what will be the position of the switch?  medium I assumed in the absence of additional info there were 3 positions  .  i.e low , med , high. any even number of flips will put the sw back on med

6. Can you arrange four nines to make it equal to 100.    99 9/9

8. If 1/2 of 5 is 3, then what is 1/3 of 10?  3.67   This is NOT a math calculation      I envisioned 1/2 of 5 = 2 1/2 + 1/2 = 3;  therefore 1/3 of 10 = 3.33 + 1/3 =3.367

9. 100 students entered college. 55 of them chose music. 44 of them chose sports. 20 of them chose both. How many of them chose neither music nor sports?   21

Of the 55 ,20 choose both leaving 35 ; of the 44 ,20 choose both leaving 24;             35 music only ;24 sports only ; 20 M&S  total=79  100 - 79 = 21 who do neither

10. Four friends are going to a concert. When they arrive, there are only five seats together left in the theater. The manager will let all four friends in for free if one of them can tell her how many different seating arrangements are possible for four people with five empty seats.     120  5 seats taken 4 at a time  5 !

All four are let in free. Could you have given the correct answer?   120    5 seats taken 4 at a time  5 !

12. At six o’clock the wall clock struck 6 times. Checking with my watch, I noticed that the time between the first and last strokes was 30 seconds. How long will the clock take to strike 12 at midnight?       5 hrs 59 1/2 minutes  NOTE: the question is not how long it chimes at 12 :00 ,but how long from the 30 seconds of chiming at 6:00

3. There are several books on a bookshelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?   9

14. John has been hired to paint the numbers 1 through 100 on 100 apartments.   my bad 20

How many times he has to paint 8?   20

15. You have two books. One of them is upside-down and the other is rotated so the top of the book is facing you.

What is the sum of the first page in each book?    1 +1   Up side down ,laying on its side ,propped at an angle the first page is 1 

16. There is a certain club which is for men only. There are 600 men who belong to this club and 5% of these men wear one earring. Of the other 95% membership, half wear two earrings and the other half wear none. How many earrings are being worn in this club?    600

17. Does a pound of gold or a pound of feathers weight more?  feathers      A pound of feathers weighs  16 ounces avoirdupois;  Gold is weighed on the troy system whereby a troy pound is 12 oz ;   1 troy oz  = 1.0971 oz avoirdupois  therefore 1 pound of gold weighs 13.1652 oz avoirdupois

18. There is a chain nailed to the wall. The chain is 10 feet long and the center of the chain dips down 5 feet from where each side of the chain is nailed to the wall. How far are the 2 ends of chain from each other?            on the same nail

19.Little Johnny is walking home. He has $300 he has to bring home to his mom. While he is walking a man stops him and gives him a chance to double his money. The man says "I'll give you $600 if you can roll 1 die and get a 4 or above, you can roll 2 dice and get a 5 or 6 on at least one of them, or you can roll 3 dice and get a 6 on at least on die. If you don't I get your $300."

What does Johnny do to have the best chance of getting home with the money?  keep on walking

20. If you have 6 women and 2 friends, how many women do each of your friends get            if the friends are two of the 6 women;i.e. women themselves , then each is entitled to herself, or one each/   If the two friends are male then no women.

 

•  
• Quote

[DejMar]

I do believe #3 --   What 3 positive numbers give the same result when multiplied and added together? -- is not grammatically correct.
I believe the question should be -- What three positive numbers give the same result when multiplied together and when added together? The adverb should not be implying each operation occurs together, but should occur for each operation as each operation is intended to be independent, yet gives the same result.

I do agree with Donald Cartmill that #12 also is not written as it should be.

Edited June 23, 2018 by DejMar
adding comment