# Records of Cooke's Service's fuel oil consumption for the last six-month period show that Cooke paid 96.1 cents per litre for the first 1,200 litres, 95.1 cents per litre for the next 1,525...

Records of Cooke's Service's fuel oil consumption for the last six-month period show that Cooke paid 96.1 cents per litre for the first 1,200 litres, 95.1 cents per litre for the next 1,525 litres, and 89.1 cents for the last delivery of 1,700 litres. Determine the average cost of fuel oil per litre for the six-month period.

Your final answer should be in cents per Litre to ONE DECIMAL PLACE.

____________ cents / L

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### 2 Answers

To find this weighted average you have to find the total combined price and then divide it by the total purchases.

The first 1200 L cost 95.1 cents/L. We multiply the amount by the cost and we get: `1200 xx 96.1= 115,320` cents for the purchase

Next we multiply the second amount 1,525 L by its unit price 95.1 cents/L to get a total price of `1525 xx 95.1=145,027.5` cents.

Then we multiply the third amount 1700 L, by its unit price of 89.1 cents/Litre and get `1700 xx 89.1=151,470` cents.

To find the average price per Litre, we add up the price of all the purchases, and divide the sum by the total litres of fuel bought.

`(115,320+145,027.5+151,470)-:(1200+1525+1700)=` `411,817.5-:4425=93.1` Cents/L

We can find the average by figuring out the total cost and dividing that by the total amount of litres.

Total cost:

First group: `1200*0.961=1153.2`

Second group: `1525*0.951=1450.275`

Third group: `1700*0.891=1514.7`

`1153.2+1450.275+1514.7=4118.175`

Divide total cost by total amount:

`4118.175/(1200+1525+1700)=0.9306`

Multiply by 100 to get cents per litre, and the answer is:

`93.1 cents`

Hope that made cents!