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The average of 8 readings is 24.2, out of which the average of first two is 18.5 and that of next three is 21.1. If the sixth reading is 5 less than seventh and 7 less than eighth, what is the sixth reading?

A.

26

B.

27

C.

26.1

D.

27.1

Answer with explanation

Answer: Option DExplanation

Here take sixth number = x , then

Seventh reading = x + 5 and 8th reading = x +7

Average of 8 readings is 24.2

Sum of 8 readings = 24.2 x 8 = 193.6

Sum of first five numbers = ( 18.5 x 2) + (21.1 x 3) = 37 + 63.6 = 100.3

Now the sum of 6th, 7th & 8th = 193.6 – 100.3 = 93.3

So ( x + x + 5 + x + 7) = 93.3

3x = 93.3 – 12 = 81.3

x = 27.1

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