Question

A number when divided by 5 leaves 3 as remainder. What will be the remainder if the square of this number is divided by 5 ?

Answer 1

let the number be x 

x=5k+3

x²=(5k+3)²

=(25k²+30k+9)

= 5(5k²+6k+1)+4

∴ the answer is 4 

dividing x² by 5 we will surely get 4 as remainder

Answer 2

Hi !

Let the no: be "a''

A.T.Q.,

a = 5p + 3

a² = (5p+3)²

    = 25p² + 30p + 9

    = 5(5k² + 6k +1 )+4

Remainder = 4

Hope this helps you !