If a : b = 2 : 3, b : c = 4 : 5 then find a : b : c.

$\begin{array}{l}a:b=2:3b:c=4:5\\ a:b:c=?\end{array}$

First equal the Ratio of b so that we have to multiply $a:b$with 4 and $b:c$with 3

$\begin{array}{l}\therefore a:b=2\times 4:3\times 4=8:12\\ b:c=4\times 3:5\times 3=12:15\\ \therefore a:b:c=8:12:15\end{array}$