Answer:
225
Explanation:
15x15=225
There is a cool trick you can do. Lets take 28 and square it.
First you round the number up. 28 rounded is 30. You rounded up by 2 (30-28=2) so you minus 2 from 28.
You are left with these two numbers, 26 and 30. Add a zero to the 26.
You now have 260 and 3 (you remove 0 on the 30 since you added it to the 26)
Then you multiply by 3.
260x3=780
Then you add the square of the number you rounded up too, which is 2.
You are left with this equation.
(2^2)+780= 784
28x28=784.
This works for numbers below 100 and integers