Problem of the Week: Blocks on a balance
You have 21 blocks, each of which weighs a rational number of ounces. Suppose that, given any 20 of the blocks, there is always some way to place them on a two-pan balance scale, 10 blocks on each pan, so that the scale is in equilibrium. Prove that the 21 blocks must all be of equal weight.
Winner
The winning solution to this problem was by Rob Brase.
