How many zeroes are there at the end of the number N, if N = 90! + 180! ? Choose the correct choice from the following answers:
A) 15  B) 18  C) 21  D) 24  E) 27
The number of zeroes at the end of 90! will be less than the number of zeroes at the end of 180!   Hence it is sufficient to calculate the number of zeroes at the end of 90!   The number of zeroes = [90/5] + [90/25] + [90/125] = 18 + 3 + 0= 
<gadget id="calculator">18 + 3 + 0</gadget>
<output>21</output>
21   The answer is 21.
<result>C</result>
How many zeroes are there at the end of the number N, if N = 90! + 180! ?