Engineers are confronted with two apparently true but contradictory statements:

a) To fly, lift must equal the weight of the airplane (Lift = Weight).

b) Commercial airliners such as Boeing 747-400 and Airbus 320 have thrust-to-weight ratios of about 0.3. i.e. Thrust / Weight = 0.3

If the engine thrust (Thrust) is 3N, then the weight must be 10 N, and the Lift must be 10 N as well.

But there is a significant problem: According to this logic, 10 N of Lift is 7 N greater than the 3 N of Thrust. This is impossible as 3 N of Thrust cannot produce the Lift of 10 N.

Hence a paradox arises, as equations (a) and (b) appear true when stated individually. But combined they produce equation (c) ‘Thrust / Lift = 0.3’ that is false (i.e. impossible).

Therefore, one of the equations (a) or (b) must also be false. But which one?

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I hope you can help me to get some constructive feedback.

I would like to introduce you to a new riddle/ quiz concept.

The Bar Race Riddle

A YouTube riddle that you can participate using the comments function.

The highlight about this puzzle is that you can see your resulting points in an exciting Bar Chart Race video.

I look forward to your constructive feedback.

Current riddle and best practice video for the riddle:

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I have come across an incredibly difficult riddle which I would like to share with you:

100 people are assigned with natural numbers between 1 and 100. These numbers are entirely random and independent of one another, meaning there can be duplicates (and consequently missing numbers). Each person receives an anonymous list of 99 numbers representing everyone else's numbers but not her own.

She then makes a guess regarding her own number based on the numbers she sees and the strategy that was agreed upon in advance by the group. They cannot communicate in any way and cannot hear what others have guessed, i.e. they are completely isolated all the way through.

The strategy they develop should guarantee that at least 1 person makes a correct guess regardless of the given numbers.

I have battled through this brain crushing puzzle, and would be glad to see your ideas and thoughts.

Cheers!

Btw, I am sorry if this riddle was already posted, I tried searching before posting.

]]>i cant for the llfe of me find the flaw with his logic.

somewhere between factoring each polynomial and the step before is wrong. but i see no mistake.

]]>I code the board as layers, columns, and items. Each rule is them translated into two layer/item pairs; for example, a textual rule can become 1C-4B. The program I have written properly executes all of the games ‘rules’ and it also looks for a single item on a layer and recognizes that that must be the item in the column in which it appears. In fact, for one super simple game, my program actually came up with the correct answer. However, as I try the more reasonable puzzles, the answer is not correct. For example, in the game Hard:#1, there are five layers and six items. Thus, a proper result would have just six ‘columns’ of results. However, the best I have been able to do is 19 columns (and in these 19 solutions are the correct six).

I am clearly missing something to eliminate the extraneous 'solutions' (which are wrong!). I have looked over this particular game in great detail, but do not see any way to use an indirect approach to help eliminate some of the wrong answers.

So, please, if you have any insights, algorithms, etc., please share. Please.

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1) What gets higher as it falls?

2) How do you stop moles from digging in your garden?

3) Why did the overweight actor fall through the theater floor?

4) What happened to the man who invented the silent alarm clock?

5) What's the best known star with a tail?

6) How did an actor get his name up in lights in every theater in the country?

7) Where would you find a square ring?

8.) What do you give a bald rabbit?

9) How do you make a slow horse fast?

10) Why did Sam wear a pair of pants with three large holes?

]]>More answers, more groans!

1) snow

2) Hide (or take) their shovels!

3) It was just a stage he was going through.

4) He was given the Nobel Prize.

5) Mickey Mouse.

6) He changed his name to Exit.

7) At a boxing arena.

8.) A hare piece.

9) Don't feed him.

10) To get his feet in (all pants have three large holes).

Original: http://brainden.com/forum/topic/11943--/

My Additions: http://brainden.com/forum/topic/12010--/

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100 pirates need to allocate 100 identical laptops among them. Their democratic system works as follows:

All pirates are ranked by their seniority (all pirates have different ranks). First, the most senior pirate proposes a plan that states exactly how many laptops each pirate gets. The 100 pirates vote on the plan and it passes at least half of the pirates vote for it. If it passes, all pirates take their laptops and go home. If it fails, the one who proposed the plan (the most senior pirate in this case) is killed, and the second most senior pirate takes his place and proposes his plan.The same process is repeated in the order of seniority until someone's plan is passed.

Assume every pirate makes his decision based on the following priorities:

1. He doesn't want to die.

2. Given he's not going to die, he would prefer to get as many laptops as possible.

3. Given he's going to get the same number of laptops, he would prefer as many other pirates to die as possible.

Also assume every pirate is logical, rational, and selfish (wants as many laptops as possible and doesn't care what anyone else gets as long as it doesn't affect him) and knows everyone else is the same. What will happen? i.e. whose proposal will be passed and what is the proposal?

]]>One day Reginald Candlenut, an auror, burst into the office of chief warden Teophilius Betelfax.

"Mr Betelfax, I fear that two prisoners have somehow found a way to communicate despite the strong measures. Thanks to the charm Amplifo Petri I heard crackling in the prison walls. I made a large number of measurements in equal intervals and found that in 45% of them there is silence, in 38% there is a single crackling sound and in the remaining 17% there are two crackling sounds."

"I wouldn't be worried, Candlenut. It seems that two stonenibblers have found refuge into our prison's walls. Stonebibblers are very rare, but as a hobbyist magizoologist I know all about them. Each stonenibbler has a personal fixed probability to be nibbling on stones at a given moment. They are exceedingly rare, but are a good explanation of your observations."

Betelfax described the stonenibblers correctly, but are they really a good explanation of Candlenut's observations? ]]>

2)What is round as a dishpan, deep as a tub, and still the oceans couldn't fill it up?

3)Scarcely was the father in this world when the son could be found sitting on the roof.

4)What goes up the chimney down, but can't go down the chimney up?

5)When one does not know what it is, then it is something; but when one knows what it is, then it is nothing.

My mind is a sieve with the holes getting bigger every day.

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See picture below:

There exist an infinite plane with infinite number of dots. For sake of argument, let's assume they are 1 inch away from each other.

However, below(on your far left) you can see 3 lines already made. The last line is the yellow one.

What you see on the right, are all combinations of possible moves. Move is defined as structure of lines until you reach an empty dot.

Thus, there are 6 combinations of single line(on top). While on bottom you see 10 combinations. 5 of them moves with 2 lines, and 5 with 3 lines.

Total # of combinations is 16.

So far so good?

Well the basic unsolved question are:

* Does formula exist to calculate total number of combinations(16 in this case) just by looking at the initial graph of 3 lines?

** Does formula exist to show the breakdown of all combinations (6 for single line, 5 for 2 lines, 5 for 3 lines?

*** is 16 the biggest number of combinations that you can make from 3 line starting configuration? For instance: Try to calculate # of combinations (1 lines, 2 lines, 3 lines) from this initial variation:

To not spoil the fun, i will just say there is more than 16. So is this the best solution? How we can prove that this is the best we can do? Obviously we can prove that just by doing all 3 line configurations by hand, but what if we take it to next level? What's the best 4 line configuration and how many combinations it has? How about 5,6.7...(n) ? The tree expands quite rapidly, and also few things need to be explained:

Combinations vs Permutations:

Above, there are 4 lines as starting configuration. In this case, there are 36 combinations OR 41 permutations. The reason is because you can go from A > B > C > D or C > B > A > D. Once again, is there a formula to calculate combinations (36) and Permutation(41) from any starting configuration?

Notation + Final info to consider:

Using above notation, you can notice that each configuration is unique and might have different #s of combinations and or permutations. For example:

Anyone with any input, either mechanical or potentially writing a code to get the answers How many combinations/Permutations for each variation with up to 10 lines as a starting configuration, would be greatly appreciated. If your program can handle bigger starting configurations, that's even better!

Thank You and enjoy!

I read this from a book and it looks a bit like a the classical "rope burning question". However, in the classical question (eg. https://tzookb.com/two-ropes-brainteaser), you are given **two **ropes where each rope takes an hour to burn from one end.

In the book I read, however, you only have **ONE **rope, so I couldn't figure out how to time 15 minutes. Could anyone figure out a way to time 15 minutes with just one rope? Could there be a mistake in the book?

1a) Always start in the square to right of center square

!) you are always traveling diagonally down to the right; when you exit the right side,you move down one row then jump left to farthermost open square

2) moving diagonally down to the right.you will exit the bottom..move one column right and jump

up to the highest open square

3)When you are trying to move down and right and you encounter a numbered square

...you go in the upper left corner and out the upper right corner ending on the same row

you started

3 a) If the above move puts you out side the main grid then you jump back to the left as far as poss on that row

3 b) If you are still inside the big grid,then you move down to the right as before

3 c) when you exit on the main diagonal Move to the left as far as possible in the bottom row

4) The above are all repetitive moves and allow you fill in any odd numbered grid such that all columns ,all rows and the diagonals add up to the same sum

I once read over the internet a question like:

You have a knife which is very sharp and a rope of unifoirm length, with a single cut what is the probability that the rope is cut exactly from half.

The who gave the answer 1/3 had the logic that there are only three possibilities of this experiment after the cut.

1. Left peice is bigger

2. right peice is bigger

3. left peice = right peice

so the probability he calculated is 1/3.

When i discussed with some of my friends they were not convinced on this answer, arguing that this type of experiment can have infinite possibilities.

Can someone please help and explain the correct answer if it exist at all.

Regards

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A friend asked me this one: What is the minimum distance from the Earth to Mars, in kilometres?

He also showed me this: 1.8668509 x 10^{-6} pc

After searching a bit I've learned that the minimum distance from the Earth to Mars is about 54.6 million kilometres, but my friend says that the answer is not correct and that I have to look to the "formula?" he showed.

I ask you to give me a hand on this one, because I'm stuck...

Thank you!

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