Prove that $\sqrt{5}$ is irrational
2. Explain why 7 × 11 × 13 + 13 and 7 × 6 × 5 × 4 × 3 × 2 × 1 + 5 are composite numbers.
3. Check whether 6n can end with the digit 0 for any natural number n.
4. Given that HCF (306, 657) = 9, find LCM (306, 657)
7. Express each number as a product of its prime factors: 140, 156, 3825, 5005, 7429