Question

Find the square of the following numbers without actual multiplication
$42$

Answer 1

Consider the given number.

$42$

We know that

${(a+b)}^2=a^2+b^2+2ab$

Therefore,

${(40+2)}^2={\left(40\right)}^2+2^2+2\times 40\times 2$

${\left(42\right)}^2=1600+4+160$

${\left(42\right)}^2=1764$

Hence, this is the answer.