Two numbers are in the ratio $5 : 7$ and their HCF is 9. What is their LCM?

Explanation

1. 01

   Since 5 and 7 have no common factor, the numbers are $5 \times 9 = 45$ and $7 \times 9 = 63$.

2. 02

   $\operatorname{LCM} = \operatorname{HCF} \times 5 \times 7 = 9 \times 35 = 315$.