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Ed has 4 cards.
There is a number on each card.
12
6
15
?
The mean of the 4 numbers on Ed's cards is 10
Work out the number on the 4th card.

Respuesta :

janmilczek

Answer:

7

Step-by-step explanation:

Let's call the missing card number "x".

The mean is the sum divided by the number of elements, so we know that:

[tex]\frac{12 + 6 + 15 + x}{4} = 10\\~\\12 + 6 + 15 + x = 40\\33 + x = 40\\x = 7[/tex]

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