Question

Shane has to fill a water tank in 3 hours 40 minutes and he used 7 pipes for that. How many pipes should he use to fill the tank in 1 hour 21 minutes?
[2 Marks]

Answer 1

Let the number of pipes be y.

$\begin{array}{ccc}\text{Number of pipes}& 7& y\\ \text{Time (in minutes)}& 220& 81\end{array}$

[1 Mark]
The number of pipes and the time are inversely proportional.

AB = constant
$A_1\times B_1$ = $A_2\times B_2$

$7\times 220=y\times 81\frac{7}{y}=\frac{81}{220}$

$\Rightarrow y=\frac{7\times 220}{81}=19.01\approx 19$

Shane has to use 19 pipes to fill the tank in 1 hour 21 minutes.
[1 Mark]