Mr Smith has lots of pound coins, ten boxes in all. Each box contains 100 pound coins, but one box contains coins which are all counterfeit and are slightly lighter, 1/16 of an ounce lighter to be exact.
The problem lies in the fact that they all look identical, the only way to tell them apart is to weigh them.
Mr Smith knows the correct weight for a box, but how many weighings are required to determine which box contains the counterfeit ones?
Hint: The answer is a lot less than 100 weighings.
Answer: One weighing is enough.
Take one coin from the first box, two from the second and so on.
When the coins are weighed, the number of 1/16ths light will tell us which box contains the counterfeits.
For example if it was box 5, the weighing would be 5/16 too light.
Hint: How many clock-minutes pass for each real hour?
Since the clock is gaining 12 minutes every hour, for every real hour that has passed, the clock will show 72 minutes.
Since the clock shows 10.00pm, we know that 22 x 60 = 1320 clock minutes have passed. 1320 ÷ 72 x 60 = 1100.
This therefore equals 1100 real minutes and hence 18 hours 20 minutes = 6:20pm.
The clock stopped 4 hours ago, therefore the time must now be 10.20pm. QED.
What is represented by this BrainBat?
erutuf eht ot
[Ref: ZQXE] Copyrighted.
Hint: Say what you see.
Answer: Back to the future.