How is it possible?
There are eight ping pong balls. One is lighter than the others, which all weigh the same. How is it possible to tell which is the lightest ball by using a balance scale only twice?
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Place three balls on one side of the scale and three on the other. If the two sides balance, then the light ball is among the remaining two and a second weighing will tell which it is. If the first weighing shows a disparity, however, take the three balls weighing the least and place one on each side of the scale, putting one to the side. If the two balance, the third is the light one. If they dont balance, you know which one is light.
Take from the pack the thirteen cards forming the suit of diamonds and arrange them in this order face downwards with the 3 at the top and 5 at the bottom: 3, 8, 7, Ace, Queen, 6, 4, 2, Jack, King, 10, 9, 5. Now play them out in a row on the table in this way. As you...