A certain number when divided by 5 leaves a remainder of 3. What is the remainder when the square of this number is divided by 5?
Q1. A certain number when divided by 5 leaves a remainder of 3. What is the remainder when the square of this number is divided by 5?
Answer: 4
Explanation: Let's denote the number as 5k + 3. Squaring it gives (5k + 3)² = 25k² + 30k + 9 = 5(5k² + 6k + 1) + 4, so the remainder is 4 when divided by 5.