You are given eight coins and told that one of them is counterfeit. The counterfeit one is slightly heavier than the other seven. Otherwise, the coins look identical. Using a simple balance scale, how can you determine which coin is counterfeit using the scale only twice?
First weigh three coins against three others. If the weights are equal, weigh the remaining two against each other. The heavier one is the counterfeit. If one of the groups of three is heavier, weigh two of those coins against each other. If one is heavier, it’s the counterfeit. If they’re equal weight, the third coin is the counterfeit.
You dance in a circle of joined hands, And though they spin away I can always see your face, In the world, no matter where I am, One look at you and I know my place.
An analogue clock is a circle, and the hands of a clock are joined at the middle. The hands can point away from you, but the clock face is always visible. No matter where you are in the world, you can probably find a clock. “One look at you and I know my place…in time!”
Thanks to Helena for creating this and sending it in.