Squaring 15, 25, 35, ..., 95

To square a two digit number ending in 5; i.e. 15, 25, 35, ..., 95, first multiply the tens digit by the next whole number and then affix 25 to it.

Example 1:

To square 15 (15^2):

The tens digit of 15 is 1 and the next whole number of 1 is 2. So:
1 * 2 = 2
Now, we affix 25 to 2. The answer is 225.


Example 2:

To square 35 (35^2):

The tens digit of 35 is 3 and the next whole number of 3 is 4. So:
3 * 4 = 12
Now, we affix 25 to 12. The answer is 1225.


Example 3:

To square 95 (95^2):

The tens digit of 95 is 9 and the next whole number of 9 is 10. So:
9 * 10 = 90
Now, we affix 25 to 90. The answer is 9025.