If 60! is written out as an integer, with how many consecutive 0's will that integer end?
6
12
14
42
56
OA 14
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heshamelaziry
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Last edited by heshamelaziry on Tue Oct 20, 2009 8:52 am, edited 1 time in total.
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..
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..
