## Welcome to BrainDen.com - Brain Teasers Forum

 Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account. As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends. Of course, you can also enjoy our collection of amazing optical illusions and cool math games. If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top. If you have a website, we would appreciate a little link to BrainDen. Thanks and enjoy the Den :-)
Guest Message by DevFuse

# Father and Son

56 replies to this topic

### #31 brhan

brhan

• Members
• 466 posts

Posted 21 March 2008 - 11:45 AM

Then using the same person 33 would work.
33 + 33 = 66
33 * 1 = 33
33 reversed = 33

60 is not the reverse of 6, 6 is the reverse of 6. If the puzzle had stated "The son's age is the father's age reversed", then 6 and 60 would have worked. 60 reversed is 06, 06 = 6

The puzzle doesn't state there should be two different people. It just says "the sum of the ages of a father and son is 66." not his son.

So, to me 33 could also be an answer.

I don't agree with your statement "60 is not the reverse of 6". Of course it is. Lets start from your last sentence. 6=06. If they are equal, reversing 6 is the same as reversing 06 -- which is 60.
• 0

### #32 brhan

brhan

• Members
• 466 posts

Posted 21 March 2008 - 11:46 AM

The sum of the ages of a father and son is 66. The father's age is the son's age reversed. Furthermore, the father's age is a multiple of the son's age. How old could they be?

1. (xy)+(yx)=66
2. k*(xy)=66
3. x+y=6
{ 24+42=66
{ .====> the answer is the son is 24, the father is 42
{ (4*6)+(7*6)=66 or 24*11/4=66

When you speak about multiples, it involves only natural numbers. Otherwise, we will not have prime numbers.
• 0

### #33 braindennewbie

braindennewbie

Junior Member

• Members
• 27 posts

Posted 21 March 2008 - 12:13 PM

60 and 6
• 0

### #34 vermontcivilwar

vermontcivilwar

Newbie

• Members
• 2 posts

Posted 22 March 2008 - 03:41 PM

Father is 44, son is 22
• 0

### #35 brhan

brhan

• Members
• 466 posts

Posted 22 March 2008 - 04:16 PM

Father is 44, son is 22

Nope. The puzzle says "the father's age is the son's age reversed!" ... failed to hold in your case. Try again
• 0

### #36 Duh Puck

Duh Puck

• Members
• 445 posts

Posted 22 March 2008 - 05:12 PM

I don't agree with your statement "60 is not the reverse of 6". Of course it is. Lets start from your last sentence. 6=06. If they are equal, reversing 6 is the same as reversing 06 -- which is 60.

I know it's silly nitpicking, but for the sake of argument, I have to agree with Mike H that the age reversal either works only in one direction, or else not at all. If we agree that the "reverse of x" is the result of writing the digits of x in the opposite order, then wouldn't it make sense that, given any input, there's only one correct way to reverse it? If so, then we can define reversal as a function, f(x) = r, where r is the reverse of x. The expected outcome then, is "of course":

f(60) = 06 ... i.e., the son's age is the reverse of the father's age
f(6) = 6 ... i.e., the father's age is NOT the reverse of the son's age

But you say that if we can accept "06 = 6" we can therefore substitute 06 for 6 as the input to the function, f(06) = 60. So the son's age is now "06"? This logic seems faulty. Removing the leading zero is a reasonable simplification, but adding them at will to the input completely breaks down the idea that reversal is a function. For example:

f(0060) = 0600 = 600 ... so the reverse of the father's age is of course 600. Does that make any sense?

I understand the statement was in there for misdirection, and it worked in my case, because I immediately ruled out any single digit possibilities, but I think that basing the misdirection on logic like this actually makes the problem less satisfying.

Edited by Duh Puck, 22 March 2008 - 05:14 PM.

• 0

### #37 brhan

brhan

• Members
• 466 posts

Posted 22 March 2008 - 10:01 PM

If we agree that the "reverse of x" is the result of writing the digits of x in the opposite order, then wouldn't it make sense that, given any input, there's only one correct way to reverse it? If so, then we can define reversal as a function, f(x) = r, where r is the reverse of x. The expected outcome then, is "of course":

f(60) = 06 ... i.e., the son's age is the reverse of the father's age
f(6) = 6 ... i.e., the father's age is NOT the reverse of the son's age

But you say that if we can accept "06 = 6" we can therefore substitute 06 for 6 as the input to the function, f(06) = 60. So the son's age is now "06"? This logic seems faulty. Removing the leading zero is a reasonable simplification, but adding them at will to the input completely breaks down the idea that reversal is a function. For example:

f(0060) = 0600 = 600 ... so the reverse of the father's age is of course 600. Does that make any sense?

I understand the statement was in there for misdirection, and it worked in my case, because I immediately ruled out any single digit possibilities, but I think that basing the misdirection on logic like this actually makes the problem less satisfying.

I think you missed one thing to include in the reverse direction -- number of digits. In our case, the number of digits were two ... b/c the sum of the ages of the father and son was 66, and we don't have negative age.

I believe including leading zero's is important. After reversing a number twice (or probably more times, according to the definition), we should be able to go back to the original number. Now, lets consider your examples:
f(60) = 06 = 6 ... I think we already on this one.
f(06) = 60 .... After reversing '60' two times, we got it back. How about if we ignore the leading zero.
f(60) = 06 = 6.
f(6) = 6 ; f(6) = 6 .... we couldn't get the original number. But for some numbers it still holds
f(23)=32 and f(32)=23

From mathematics point of view, this is not well defined. I might be wrong but that is how I see it. By the way, I am not a mathematician some of the terms I just used them loosely.
• 0

### #38 Duh Puck

Duh Puck

• Members
• 445 posts

Posted 23 March 2008 - 04:31 PM

I think you missed one thing to include in the reverse direction -- number of digits. In our case, the number of digits were two ... b/c the sum of the ages of the father and son was 66, and we don't have negative age.

I believe including leading zero's is important. After reversing a number twice (or probably more times, according to the definition), we should be able to go back to the original number. Now, lets consider your examples:
f(60) = 06 = 6 ... I think we already on this one.
f(06) = 60 .... After reversing '60' two times, we got it back. How about if we ignore the leading zero.
f(60) = 06 = 6.
f(6) = 6 ; f(6) = 6 .... we couldn't get the original number. But for some numbers it still holds
f(23)=32 and f(32)=23

From mathematics point of view, this is not well defined. I might be wrong but that is how I see it. By the way, I am not a mathematician some of the terms I just used them loosely.

At a minimum, I have to give you credit for making a compelling argument. If we assume that we should be able to get the original number back, then the simplification of removing the leading 0s from the result is superfluous; hence f(60) = 06, end of story, not f(60) = 06 = 6. Of course, we're debating rules that don't really exist in standard mathematics, since we're concerned with visual representation rather than actual value, and thus a lot of the reasoning that both of us have presented doesn't really have much of a foundation to stand on. I still think it's a bit of a stretch to say you can reverse the son's age to get the father's age, but what if we could presume some undefined rule which says something like: "In the case of reversal, the number of digits for both the input and the output has to be the same, and thus the total number of digits is the maximum of the expected input or output."? In that case I think your reasoning could stand. I still don't really agree, but since the concept of "reversal" just doesn't conform to the usual rules, I guess there's some room for latitude.
• 0

### #39 brhan

brhan

• Members
• 466 posts

Posted 24 March 2008 - 04:17 PM

At a minimum, I have to give you credit for making a compelling argument. If we assume that we should be able to get the original number back, then the simplification of removing the leading 0s from the result is superfluous; hence f(60) = 06, end of story, not f(60) = 06 = 6. Of course, we're debating rules that don't really exist in standard mathematics, since we're concerned with visual representation rather than actual value, and thus a lot of the reasoning that both of us have presented doesn't really have much of a foundation to stand on. I still think it's a bit of a stretch to say you can reverse the son's age to get the father's age, but what if we could presume some undefined rule which says something like: "In the case of reversal, the number of digits for both the input and the output has to be the same, and thus the total number of digits is the maximum of the expected input or output."? In that case I think your reasoning could stand. I still don't really agree, but since the concept of "reversal" just doesn't conform to the usual rules, I guess there's some room for latitude.

Well, I just thought the leading zeros will enable us to determine uniquely the reverse of a number. f(06)=60 and f(006)=600. Otherwise, I agree with you that if you know the number of digits in advance (like in our case) the leading zeros can be omitted.
• 0

### #40 Lost in space

Lost in space

Senior Member

• Members
• 4009 posts

Posted 24 March 2008 - 11:47 PM

Brhan, I like your posts and work, have to gripe
0=0
00=0
000= guess

But only the first is REAL (proper - as in place holder or number).
You would not say that the answer is a four digit number (0000)

therefore 06 is improper. Like the idea though.
• 0

#### 0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users