# The mean of 3 numbers is 7. The mean of 4 other numbers is 8. The mean of 5 other numbers is 11. What is the mean of all 12 numbers?

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To work out the mean (what we understand as the 'average') we do the following;

As with other formulae in this form, we have 3 ways in which it can be used.

Remember that we may add **Totals** , we may add **Numbers** , but we may NOT ADD MEANS!

**The mean of 3 numbers is 7** .

**The mean of 4 numbers is 8**

**The mean of 5 number is 11**

We can add numbers:

We can add totals:

We can find the mean of the 12 numbers:

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Let

where,

Then, the mean

We have,

Hence,

**Lyn.** !

Enjoy Maths.!

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