Question

The price of petrol goes up by $20$%. By how much per cent must Ajay reduce his consumption of petrol so that the expenditure on petrol remains the same?

Answer 1

previous price of petrol = $x$

new price $=x+\frac{20}{100}x=1.2x$

previous consumption $=y$

new consumption $=ny$

$\therefore$ expenditure $=$ same $\Rightarrow$

$\left(x\right)\left(y\right)=\left(1.2x\right)\left(ny\right)$

$n=\frac{5}{6}$

$\therefore$ petrol consumption reduced by $1-n=\frac{1}{6}$

$=\frac{100}{6}\%$

$=16.67\%$