15 replies to this topic

[Ancient Dragon]

Do you like brain teasers?

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A brain teaser is a form of puzzle that involves cogitating or mental/cognitive activity to solve. Normally, this includes thinking in unconventional ways with given constraints in mind; sometimes, it also involves lateral thinking. Logic puzzles and riddles are specific types of brain teasers.

One of the earliest known brain teaser enthusiasts was the Greek mathematician Archimedes.[1] He devised mathematical problems for his peers to solve.

Although I love brain teasers I certainly do not consider myself anywhere near an expert at solving them. So here is a teaser that I learned many years ago. It involves no (or very little) math and can be solved by simple logic.

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A king had 10 slaves. Each slave made a unique design trinket made of exactly one ounce of gold (substitute grams if you are more comfortable with the metric unit of measure). One day the king was told that one of his slaves was stealing gold by making his trinkets a little less than one ounce and pocketing the rest.

With only one weighing (on scales of some kind) how can the king determine who is the thief?

[zeroradius]

I love puzzles but i'm no good at them. I will give this one a crack.

Useing a set of balance scale take turns adding a trinket to one side and a 1 ounce weight to the other. While continuing this pattern eventualy the scales will no longer be balanced (while both trinket and counter weight reside on oposite sides of the scales), whatever the last trinket added was at the time of the unbalance is the one stealing the gold. This constitutes as one weighing because the goal was to weigh them all at once you discovered the problem while adding the matirials for one weighing. lol probably wrong but oh well (^_^)

[amrosama]

try1:
cant we just throw them all in the water at the same time and the last trinket that reaches the bottom is the fake one? probably not i guess
try2:
put all the trinkets on the scale and remove one trinket at a time and write down the weight of weight of the trinket by subtracting the weight before removing the trinket and weight after removing it

[zeroradius]

your first one wont work amrosama. The trinkets are all diffrent so depending on the design drag would effect them all diffrently. Your second one is simular to mine so i hope its right.

[amrosama]

different design but same weight??

[zeroradius]

yes but the design matteres, imagine one is rather flat with golden wings and one is a rounded ball. Even if the ball weighed slightly less (not a big diffrence, just ever so slightly) thanks to arrow dynamics the ball would hit the bottom of the container holding the water first. The reason is that the water will catch under the "wings" of the flat trinket and cause it to fall at a slower rait. Think of it like a bird. If a bird has its wings extended and does not move them at all what happens? The bird falls but it glieds downwards. What happens if the bird tucks its wings in? it falls at a much greater speed right? the same is true with these trinkets in water. This holds true for any object, there is a reason race cars look so sleek and dynamic; its not because it looks awsome.

[wim DC]

Different weight, but the different design will cause different trinkets to have different water resistance while moving towards the bottom. Potentially causing trinkets with less weight to go down faster than others.

[Ancient Dragon]

So far all answers are incorrect.

>>Using a set of balance scale take turns adding a trinket to one side and a 1 ounce weight to the other. While continuing this patter
That is incorrect because you get only one shot at the weighing of all trinkets. Your solution takes 10 weighings (one for a trinket for each slave).

Ok, here's the correct solution: Take one trinket from Slave #1, two from Slave #2, three from Slave #3 ... and 10 trinkets from Slave #10. If everyone was honest, the trinkets should weight 1+2+3...+10 = 54 ounces.

Assuming the thief was stealing 1/10th of an ounce of gold, If the first thief was the thief then the trinkets would weigh 53.9 ounces. If the second slave was the thief then the trinkets would weight 53.8 ounces, etc.

[zeroradius]

I was trying to avoid math (X.x)

Heres an easy one for you.

A boat is in a river. The boat has a small ladder on the back with 5 rungs. The rungs are set with a 1 ft gap between each one. At 5:00 am one rung is under water. the lake will rise 4.5 inches every hour untill noon. at noon the water will begin to go down by 1.6 inches every 20 minutes. At 3:26 pm how many rungs will be under the water.

[amrosama]

zeroradius said:

yes but the design matteres, imagine one is rather flat with golden wings and one is a rounded ball. Even if the ball weighed slightly less (not a big diffrence, just ever so slightly) thanks to arrow dynamics the ball would hit the bottom of the container holding the water first. The reason is that the water will catch under the "wings" of the flat trinket and cause it to fall at a slower rait. Think of it like a bird. If a bird has its wings extended and does not move them at all what happens? The bird falls but it glieds downwards. What happens if the bird tucks its wings in? it falls at a much greater speed right? the same is true with these trinkets in water. This holds true for any object, there is a reason race cars look so sleek and dynamic; its not because it looks awsome.

oxano said:

Different weight, but the different design will cause different trinkets to have different water resistance while moving towards the bottom. Potentially causing trinkets with less weight to go down faster than others.

unless the trinket moved vertically like "|" instead of "--" towards the water which will happen becuase theres no such thing as 100% flat object

[zeroradius]

once it hits the water the chances of it staying in any one position is slim. so it would still have drag.

[amrosama]

100% agree
what was the brain teaser again? lol