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The average of a set of numbers A is 85 and the average of a set B is 64. If set A has...

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timw996 | Student, Grade 10 | Salutatorian

Posted September 3, 2013 at 5:35 PM via web

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The average of a set of numbers A is 85 and the average of a set B is 64. If set A has 4 times as many elements as set B, what is the average value of all the elements in both the sets.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted September 3, 2013 at 5:40 PM (Answer #1)

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Set A has 4 times as many elements as set B. The average value of the elements of set A is 85 and the average value of the elements of set B is 64.

Let N denote the number of elements in set B, the number of elements in set A is 4*N. The total number of elements in both the sets put together is 5*N.

The total value of the elements of set A is 340*N and the total value of the elements of set B is 64*N. This gives the required average as `(340*N + 64*N)/(5*N) = 80.8`

The required average is 80.8

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