Question

The unit digit of the square of a number whose unit digit is 5, is ___ .

Answer 1

If the unit digit of a number is '5', then the square of that number ends with the unit digit '5'.

For example, $5^2=25$, ${15}^2=225$, ${25}^2=625$, ${35}^2=1225$ etc. all ends with the digit '5'.