Average Salary
12 Sep 2008
Puzzle

Four honest and hard-working computer engineers are sipping coffee at Starbucks. They wish to compute their average salary. However, nobody is willing to reveal an iota of information about his/her own salary to anybody else. How do they do it?

Source

Heard from a fellow student at UC Berkeley in 1996.

Solution

The first engineer picks a random k-digit integer for some large k, adds his salary to it and writes the sum on a chit. The chit is passed around. When it returns to the first engineer, he subtracts the k-digit integer.

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