You're on the right track, but remember - the question asks for the quantity of petrol purchased. You chose the right numbers though.

Say the price of petrol is normally $100/unit. A 25% increase would raise the price to $125/unit. Kevin will only spend 15% more or $115. You did the math right too. You find that you can only buy $115/($125 per unit) = 0.92 units of petrol with your $115.

Instead of having 1 unit of petrol, you have 0.92 units of petrol. This is an 8% decrease in the quantity - D.

let 1 litre of petrol be 100
with 25% increase, petrol is now 125/litre
kevin intends to spend only 115/litre

therefore we have ,

115/1 : 125/1
crosss multiplying we will arrive at 115/125 = 0.92 ( 8 % decrease in the quantity of petrol)

IMO:D

romitvsingh wrote:) If the price of petrol increases by 25% and Kevin intends to spend only an additional 15% on petrol, by what percentage must he reduce the quantity of petrol purchased?

Possible AnswersSelected Possible Answer
A. 6.67%

B. 12%

C. 10%

D. 8%

E. 14%

Let Initial figures be as follows -


Price - 10/lit

Quantity Purchased is - 10 lit

Amount/Expenses - 100


After increase -

Price - 12.5

Quantity - x

Amount - 115 ( including the increase of 15% in salary)



So , 12.5 * x = 115

Or, x = 9.2


So quantity of petrol to be purchased decreases by ( 10 to 9.2 ) 0.8


Hence % decrease in consumption of petrol is -

(.8/10 )*100 % => 8%