2nd Brazil 1980 Problem 1 Box A contains black balls and box B contains white balls. Take a certain number of balls from A and place them in B. Then take the same number of balls from B and place them in A. Is the number of white balls in A then greater, equal to, or less than the number of black balls in B?
Equal. Solution Suppose we move n balls from A to B, then x white balls from B and n-x black balls from B. That leaves x black balls in B. So both numbers equal x. 2nd Brazil 1980 © John Scholes jscholes@kalva.demon.co.uk 23 Oct 2003 Last corrected/updated 23 Oct 03