If $a : b = 2 : 3$ and $b : c = 4 : 5$, what is $a : c$?

Explanation

1. 01

   $\frac{a}{c} = \frac{a}{b} \times \frac{b}{c} = \frac{2}{3} \times \frac{4}{5} = \frac{8}{15}$.

2. 02

   So $a : c = 8 : 15$.