Tough Question

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by aakar » Tue Oct 20, 2009 7:49 am
To find the number of zeros in x!, find out how many factors of 5 are in x!..

1x2x3x4x5.......x10...x15...x20..x25.
Numbers 1-5: 1 factor of 5 (5)
6-10: 1 factor of 5 (10)

All the way up to 60. But remember that 25 (5*5) and 50 (5*5*2). So 60/5 = 12 + 2 = 14

Remember that the 2 accounts for the 2 extra factors of 5 that appear in 25 and 50..