A certain number when divided by 7 leaves a remainder of 3. What is the remainder when the square of this number is divided by 7?
Q1. A certain number when divided by 7 leaves a remainder of 3. What is the remainder when the square of this number is divided by 7?
Answer: 2
Explanation: Let's denote the number as N = 7k + 3. N² = (7k + 3)² = 49k² + 42k + 9 = 7(7k² + 6k + 1) + 2. So, the remainder when N² is divided by 7 is 2.