Question

Find the square of $31$.

Answer 1

We can calculate the square directly by multiplying 31 by itself; But there is an easier method.

We know the difference of the squares of two consecutive natural numbers is equal to the sum of the two numbers. That means,

${31}^2-{30}^2=31+30$

we know that ${30}^2=900$
So, ${31}^2=900+31+30=961$