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

A. 18 B. 22 C. 25 D. 27 Answer: Option C
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### Solution(By Apex Team)

Let the eight number be x Then, sixth number = (x – 7) Seventh number = (x – 7) + 4 = (x – 3) So, \begin{aligned}&\Leftrightarrow\left(2\times15\frac{1}{2}\right)+\left(3\times21\frac{1}{2}\right)+(x-7)+(x-3)+x=8\times20\\ &\Leftrightarrow31+64+(3x-10)=160\\ &\Leftrightarrow3x=75\\ &\Leftrightarrow x=25\end{aligned}

## Related Questions On Average

A. 20
B. 21
C. 28
D. 32
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A. 18
B. 20
C. 24
D. 30
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A. 10 years
B. 10.5 years
C. 11 years
D. 12 years
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### If the arithmetic mean of 0, 5, 4, 3 is a, that of -1, 0, 1, 5, 4, 3 is b and that of 5, 4, 3 is c, then the relation between a, b, and c is.

A. a = b = c
B. a : b : c = 3 : 2 : 4
C. 4a = 5b = c
D. a + b + c = 12
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