Question

The cost of petrol rises by 2 cents a liter. last week a man bought 20 liters at the old price. This week he bought 10 liters at the new price. Altogether, the petrol costs $9.20. What was the old price for 1 liter?

Answer 1

The old price was $0.30/liter.

Explanation:

The original price of petrol was x dollars per liter.

The new price is x + 0.02 dollars per liter.

Last week he bought 20 liters, so he spent 20x.

This week he bought 10 liters, so he spent 10(x + 0.02).

The total he spent in the two weeks is 20x + 10(x + 0.02).

The total he spent is $9.20.

20x + 10(x + 0.02) = 9.20

20x + 10x + 0.2 = 9.2

30x = 9

x = 0.3

The old price was $0.30/liter.

Answer 2

a = 30 (cents)

Explanation:

30 cents.

20 x a + 10 x (a+2) = 920 (cents)

20 x a + 10 x a + 20 = 920

30 x a + 20 = 920

30 x a = 920 - 20

30 x a = 900

a = 900 : 30

a = 30 (cents)