Question

It is given that, $p$ is inversely proportional to $y$,

If $p=1.2$ when $y=100$, calculate:
the value of $p$ when $y=4$
the value of $y$ when $p=3$

Answer 1

$p\propto \frac{1}{y}\left(\text{Given}\right)$

Therefore,

$\frac{p_1}{p_2}=\frac{y_2}{y_1}$

Now,

$p_1=1.2$

$y_1=100$

Therefore,

• When $y=4$

$p_2=?$

$y_2=4$

$\therefore \frac{1.2}{p_2}=\frac{4}{100}$

$\Rightarrow p_2=1.2\times 25=30=p$

When $p=3$

$p_2=3$

$y_2=?$

$\therefore \frac{1.2}{3}=\frac{y_2}{100}$

$\Rightarrow y_2=0.4\times 100=40=y$

Hence when $y=4$, value of $p$ is $30$ and when $p=3$, value of $y$ is $40$.