Question P6 An average is a total
The mean of four numbers is 18. Three of the numbers are 15, 20, and 22. Find the fourth number.
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Turn the average back into a total before doing anything with it.
In this one. A mean is the total shared out equally, so multiplying it back by how many there are recovers the total — and once you have the total, an unknown member is just what is left after subtracting the ones you know.
The word 'average' appears alongside a group being split into two parts, or two separate journeys or trips being combined into one overall figure.
Children average two averages directly, such as averaging two speeds or two group averages, without weighting by how many, or how long, each part actually covers.
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