a) The average amount per purchase is a simple average: The total amount of the purchases (58+69+71+56) divided by the total number of purchases (4). `(58+69+71+56)-:4=254-:4=63.50` Litres

b) The price per Litre of all the purchases is a weighted average. You find that by finding the combined prices and dividing by the combined Litres bought. You find the combined prices by multiplying the number of litres by its unit price. `(58 L)/1 xx (128.7 cents)/L=7,464.6 cents`

`(69L)/1 xx (132.2 cents)/L=9,121.8cents`

`(71 L)/1 xx (122.6 cents)/L=8,704.6cents`

`(56L)/1 xx (133.4 cents)/L=7,470.4cents`

Then we divide the total cents by the total Litres to find the average price per Litre

`(7,464.6+9,121.8+8,704.6+7,470.4)-:(58+69+71+56)=` `32,761.4-:254=128.98` cents/L

c) This is a simple conversion, cross cancelling units.

`(128.98 cents)/L xx (1L)/(9.68 km)=13.32`cents/km