How many trailing zeros are there in 55! ?

To find the number of trailing zeros in 55!, we need to find the number of factors of 10 in the factorial. A factor of 10 is made by multiplying 2 and 5. In a factorial, there are always more factors of 2 than 5. So, we just need to count the number of factors of 5 in 55!.

Step 1: Divide 55 by 5. The result is 11. This means there are 11 numbers in 55! that have 5 as a factor.

Step 2: However, some numbers in 55! have more than one factor of 5. For example, 25 has two factors of 5 (because 25 = 5*5). So, we need to count these extra factors. We do this by dividing 55 by 25. The result is 2. This means there are 2 numbers in 55! that have an extra factor of 5.

Step 3: Add the results from step 1 and step 2. This gives us 11 + 2 = 13.

So, there are 13 trailing zeros in 55!.