Question

Find the squares of the following numbers:

(3) 75

Answer 1

The square of any number ending with 5 can be written as:
(a5)² = [a × (a + 1) × 100] + 25
Here, a is the number excluding the units digit.
So, the square of 75 can be calculated as:
[7 × (7 + 1) × 100] + 25
= [7 × 8 × 100] + 25
= 5600 + 25
= 5625