On dividing a number by 5, we get 3 as remainder. What will the remainder when the square of the this number is divided by 5 ?

Question:
On dividing a number by 5, we get 3 as remainder. What will the remainder when the square of the this number is divided by 5 ?

[A].

0

[B].

1

[C].

2

[D].

4

Answer: Option D

Explanation:

Let the number be x and on dividing x by 5, we get k as quotient and 3 as remainder.

    x = 5k + 3

    x2 = (5k + 3)2

   = (25k2 + 30k + 9)

   = 5(5k2 + 6k + 1) + 4

On dividing x2 by 5, we get 4 as remainder.