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The average (arithmetic mean) of seven numbers is 9 and the average of

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Bunuel
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The average (arithmetic mean) of seven numbers is 9 and the average of [#permalink] The average (arithmetic mean) of seven numbers is 9 and the average of   12 May 2022, 03:45
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The average (arithmetic mean) of seven numbers is 9 and the average of three of these numbers is 5. What is the average of the other four numbers?

A. 4
B. 5
C. 7
D. 10
E. 12
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E
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Re: The average (arithmetic mean) of seven numbers is 9 and the average of [#permalink] The average (arithmetic mean) of seven numbers is 9 and the average of   12 May 2022, 06:02
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If the average of the seven numbers is 9, they must add up to 63.

And if the average of the first three numbers is 5, they must add up to 15.

That means that the other four numbers must add up to \(63-15\), or 48.

The average of these four numbers is the sum divided by the count, so \(\frac{48}{4}\), which is 12.

Answer choice E.
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Re: The average (arithmetic mean) of seven numbers is 9 and the average of [#permalink] The average (arithmetic mean) of seven numbers is 9 and the average of   01 Aug 2022, 00:05
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Theory

    ➡ Average = Sum of all the Values / Total Number of Values
    ➡ Sum of All the values = Average * Total Number of Values

The average (arithmetic mean) of seven numbers is 9

Sum of 7 numbers = Average * 7 = 9*7 = 63

The average of three of these numbers is 5

Sum of 3 numbers = Average * 3 = 5 * 3 = 15

The average of the other four numbers

Average = Sum of 4 numbers / 4 = Sum of 7 numbers - Sum of 3 numbers/4 = \(\frac{63 - 15 }{ 4}\)
= \(\frac{48}{4}\) = 12

So, Answer will be E.
Hope it helps!

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Re: The average (arithmetic mean) of seven numbers is 9 and the average of [#permalink]
01 Aug 2022, 00:05
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