waecmaths question:
If $3p=4q$ and $9p=8q-12$ find the value of pq
Option A:
12
Option B:
7
Option C:
−7
Option D:
−12
waecmaths solution:
\[\begin{align} & 3p=4q---(i) \\ & p=\frac{4q}{3} \\ & 9p=8q-12---(ii) \\ & \text{Substitute }\frac{4q}{3}\text{ for }p\text{ in }(ii) \\ & 9\left( \frac{4q}{3} \right)=8q-12 \\ & 12q=8q-12 \\ & 12q-8q=-12 \\ & 4q=-12 \\ & q=-3 \\ & \text{Substitute }-3\text{ for }q\text{ in }p=\frac{4q}{3} \\ & q=\frac{4(-3)}{3}=-4 \\\end{align}\]
maths year:
maths topics: