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 ?
Options:
A .  0
B .  1
C .  2
D .  4
E .  None of these
Answer: Option D 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 ⇒ x2 = (25k2 + 30k + 9) ⇒ x2 = 5 (5k2 + 6k + 1) + 4 ∴ On dividing x2 by 5, we get 4 as remainder
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