Math CentralQuandaries & Queries


Question from morgan, a student:

if I have to multiply 1*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18*19*20 how many terminal zeros do i get?


To get a 0 on the end of your product you need to multiply a 2 and a 5. There are a lot more 2's in your product than 5's so you need only count how many 5's there are that can be paired up with a 2. There's a 5 in the 5, a 5 in the 10, ... .


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