40, 45, 45, 50, 50, 60, 70, 75, 95, 100

You can use deviations to find the mean here.

Assume that the mean is 60 since it's kind of in the middle.

Now notice that 50 is 10 less than 60 and 70 is 10 more so ignore both.
Now 40, 45, 45, and 50 together are 60 away from 60 while 75, 95, and 100 are 90 away from 60.

So we have a total of 90 - 60 = 30 deviation from 60. Since there are 10 numbers, the average must be 30/10 = 3 more than 60 i.e it must be 63.

Answer: B