Question

If $\frac{n}{n+15}=\frac{4}{9}$, then n = ?

(a) 4

(b) 6

(c) 9

(d) 12

Answer 1

$\frac{n}{n+15}=\frac{4}{9}9n=4n+60\text{(By cross multiplication)}9n-4n=60\Rightarrow 5n=60\Rightarrow n=\frac{60}{5}=12n=12$