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? 2. Teachers divide

Answer 1

Answer: the old price for 1 liter is $0.3

Step-by-step explanation:

Let x represent the old price for 1 liter of petrol.

Last week a man bought 20 liters at the old price. This means that the total amount that the man paid for 20 liters is 20x.

The cost of petrol rises by 2 cents a liter. This means that the new price per liter is x + 2/100 = x + 0.02

This week he bought 10 liters at the new price. This means that the total amount that the man paid for 10 liters is

10(x + 0.02)

= 10x + 0.2

Altogether, the petrol costs $9.20. This means that

20x + 10x + 0.2 = 9.2

30x + 0.2 = 9.2

30x = 9.2 - 0.2

30x = 9

x = 9/30

x = 0.3