M4maths Previous Puzzles

05 Oct 2009 31 zero..

Upto how many integers we should take the product 1*2*3*4*5.......... to make 31 zeros at last of the number.

OPtion

1) 140
2) 130
3) 115
4) 110
5) 100
6) 105
7) 135
8) 125
9) 145
10) 120

Solution

For obtaining 31 zeros at last of the number, 31 powers of 5 is necessary. Product 1*2*3*4*5�����upto 125
contain 5, 10 ,15���. 125. These 25 numbers are multiple of 5, besides it 25, 50, 75, 100, 125 contain
a second 5 and 125 contains a third 5 hence total number of 5 = 25+5+1 = 31

Correct Option: 8 Best Solution (0)