What is the standard deviation of the times listed below: 10, 11, 12, 10.5, 11.25, 12.25, 10.

The mean of the data is 11

now we find the difference between the mean and each number
1, 2, 3, 0.5, 0.25, 1.25, 1. 

now we square the numbers 
1, 4, 9, 0.25, 0.0625, 1.

now we find the mean of the new numbers
which is 2.1875

2.1875 is your standard deviation.