The average of 8 numbers is 20 The average of first…

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The average of 8 numbers is 20. The average of first two numbers is $$15\frac{1}{2}$$ and that of the next three is $$21\frac{1}{3}$$ . If the sixth number be less than the seventh and eighth numbers by 4 and 7 respectively, them the eighth number is :

  1. A. 18
  2. B. 22
  3. C. 25
  4. D. 27

Answer: Option C

Here is complete explanation of The average of 8 numbers is 20 The average of first….

Solution(By ExamCraze Team)

Let the sixth number = x
Then the seventh = x + 4
And the eighth = x + 7
According to the question,
$$ Rightarrow 2 times frac{{31}}{2} + 3 times frac{{64}}{3} + x + x + 4 + x + 7$$        = 8 × 20
$$eqalign{ & Rightarrow 31 + 64 + 3x + 11 = 160 cr & Rightarrow 106 + 3x = 160 cr & Rightarrow 3x = 54 cr & Rightarrow x = 18 cr} $$
∴ Eighth number x + 7 = 18 + 7 = 25

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