# Mean balance

Given information about the mean, can you work out the missing numbers?

## Problem

The mean of the set of numbers 8, 4, 5, 4,

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If another

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What numbers do

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*This problem is adapted from the World Mathematics Championships*

## Student Solutions

If

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If

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But adding another

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*Alternatively:*

If the mean of the seven numbers is 6, they must add up to 42.

If the mean of eight numbers is 6, they must add up to 48.

Therefore the eighth number is 48 - 42 = 6

If the mean of the seven numbers is 6, they must add up to 42.

If the mean of eight numbers is 6, they must add up to 48.

Therefore the eighth number is 48 - 42 = 6

So the mean of the set of numbers 8, 4, 5, 4,

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That means that ( 8 + 4 + 5 + 4 +

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so 8 + 4 + 5 + 4 +

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so 33 +

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So

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