The mean of five numbers is 5. If one of the numbers is removed from the group, the mean of the remaining four numbers is 4.25. What number was removed from the group?
The number that was removed is 4*5 - 4*5.25 = 3.
[5 * 5] - [4 * 4.25] = 25 - 17 = 8 - was removed
