The square of 42 is:

The correct answer is Option (4) → 1764

Write 42 as \(40+2\) and use \((a+b)^2=a^2+2ab+b^2\), which turns the square into easy round-number products.

• \(42^2=(40+2)^2=40^2+2\times40\times2+2^2\)

• \(=1600+160+4\)

• \(=1764\)