Easily square numbers from 901 to 999.
Example
{% scaleimage l314_example.png %}
Step 1
Subtract the number from 1000.
1000 - 995 = 5
Step 2
Square the result of step 1.
{% scaleimage l314_step2.png %}
If the result in step 2 is less than 100 then add a zero to the beginning.
025
Step 3
Subtract the result in step 1 from the original number.
995 - 5 = 990
Step 4
Place the result in step 2 behind the result in step 3
990025