Frankenstein's Revenge

A source in the Math Department, who preferred to remain anonymous, told us there was a way to cheat on Ernestine - to make calls without getting billed. Some bright boys over at Kiewit ("computer jocks," he called them) analyzed the numbers Ernestine identifies as account numbers and cracked the code. We don't know very much about math, but this is what we made of his explanation: They noticed that each account number is made up of five digits and that the sum derived by assigning alternate plus and minus values to the digits is always congruent to some number (which we won't disclose) "modular ten." He explained that numbers are said to be congruent modular ten if their difference is divisible by ten.

We thought we had a hot story, so we asked Vice President Morgan if it wasn't possible to forge account numbers. He surprised us by saying "Oh, yes, it happened the second day.... We can't have all these bright-eyed computer people around here without some of them cracking the code, but we aren't particularly worried about it." When we asked why, he said, "We have our ways of finding out who makes the calls. Several students have already been reported to the dean." He wouldn't elaborate as to how the scoundrels were caught and when we asked Bob Barnum he wouldn't tell us, either.