Ratio and Proportion — MATHS STD 7 — Question

2. 8 : 15

Solution:

As, $\text{a}:\text{b}=4:5$

$\Rightarrow\frac{\text{a}}{\text{b}}=\frac{4}{5}$

Also, $\text{b}:\text{c}=2:\text{3}$

$\Rightarrow\frac{\text{b}}{\text{c}}=\frac{2}{3}$

So, $\text{a}:\text{c}=\frac{\text{a}}{\text{c}}$

$=\frac{\text{ab}}{\text{bc}}$

$=\frac{\text{a}}{\text{b}}\times\frac{\text{b}}{\text{c}}$

$=\frac45\times\frac23$

$=\frac{8}{15}$

$=8:15$

Hence, the correct alternative is option (b).