If 25*24*23 ...*13*12*11 is expanded, how many zeros are there at the end of the answer?
There will be as many zeros at the end of the answer as there are factors of 10
in the answer.
To find the number of factors of 10, find the number of factors that are 5
and the number of factors that are 2.
25 = 5x5
20 = 5x4
15 = 5x3
So, there are 4 factors of 5.
There are more than 4 factors of 2, so there are a total of 4 factors of 10.
Therefore, there will be four zeros at the end of the answer.