The total mass of 5 boxes of oranges is 285 kg. Another box of oranges, which has a mass of 45 kg, is added to the group. What is the average mass of the 6 boxes of oranges?
- 55 kg
- 57 kg
- 330 kg
- 48 kg
Need a hint?
First, find the new total mass of all the boxes. Then, divide this new total by the new number of boxes.
Worked answer
- Find the new total mass of all the boxes: 285 kg + 45 kg = 330 kg.
- Find the new number of boxes: 5 + 1 = 6.
- Calculate the average mass by dividing the new total mass by the new number of boxes: 330 kg ÷ 6 = 55 kg.
Answer: 55 kg
The mistake this question tests
Habit
Average and total
A common mistake is to add the new box's mass to the original total and then divide by the original number of boxes (330 ÷ 5 = 66), forgetting that the number of items has also increased.
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See the answer →Practise PSLE whole numbers until the mistakes stop.
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