Question

What will be the unit digit of the squares of the following numbers?
$81$
$272$
$799$

Answer 1

The unit digit of the squares of the given numbers is shown against the number in the following table.

$\begin{array}{ccc}\text{Number}& \text{Unit digit of a square number}& \text{Reason}\\ 81& 1& 1\times 1=1\\ 272& 4& 2\times 2=4\\ 799& 1& 9\times 9=81\end{array}$