waecmaths question:
If the ratio x : y = 3 : 5 and y : z = 4 : 7, find the ratio x: y : z
Option A:
15 : 28 : 84
Option B:
12 : 20 : 35
Option C:
3 : 5 : 4
Option D:
5 : 4 : 7
waecmaths solution:
$\begin{align} & \frac{x}{y}=\frac{3}{5} \\ & x=\frac{3y}{5} \\ & \frac{y}{z}=\frac{4}{7} \\ & z=\frac{7y}{4} \\ & x:y:z=\frac{3y}{5}:y:\frac{7y}{4} \\ & \text{Multiply through by }20 \\ & 20x:20y:20z=12y:20y:35y=12:20:35 \\ & \text{Option B} \\\end{align}$
maths year:
maths topics: