Given $\displaystyle 20$ pairwise distinct positive integers each less than $\displaystyle 70$. Prove that among their pairwise differences there are at least four equal numbers.

- Mar 12th 2012, 10:07 PMabhishekkgppairwise differences of 20 +ve int. all < 70. At least 4 are equal.
Given $\displaystyle 20$ pairwise distinct positive integers each less than $\displaystyle 70$. Prove that among their pairwise differences there are at least four equal numbers.