rust8y Posted January 14, 2006 Posted January 14, 2006 The integers 1,2,3,...,100 are written on the board. What is the smallest number of these integers that can be wiped off so that the product of the remaining integers ends in 2?
matt grime Posted January 14, 2006 Posted January 14, 2006 The product is even. If it ends in 2 we're done, and the answer is 0. If not, well, just think about how to divide out to make it end in 2.
Connor Posted January 14, 2006 Posted January 14, 2006 well, for one thing there can be no multiples of five, because there would be no possibility of ending in 2... There's probably an elegant way to figure this out but I don't see it yet
matt grime Posted January 14, 2006 Posted January 14, 2006 Just work mod 10, that's easier than my first suggestion, actually.
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