Question

If the price of gasoline increases by 25% and Ron intends to spend only 15% more on gasoline, by what % should he reduce the quantity of petrol that he buys?

Answer 1

8%

Explanation:

Suppose Ron buys quantity of gasoline today `=x`
Let today's price of gasoline be equal to `=y`
Ron spends on gasoline today `=xy`

The new price of gasoline is (increase by `25%`)`=1.25xxy`
Ron wants to spend only `15%` more,
`:.`he wants to spend`=1.15xxxy`
Quantity he buys at new rate`=(1.15xxxy)/(1.25xxy)=(1.15x)/(1.25)`
Reduction in quantity of purchase`=x-(1.15x)/(1.25)=(0.10x)/1.25`
% Reduction in quantity of purchase of gasoline `=((0.10x)/1.25)/x xx100`
`=0.10/1.25 xx100=8%`