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The average of eight numbers is 20. If the sum of first two numbers is 31, the average of the next three numbers
is 21 1 and the seventh and eighth numbers exceed the sixth number by 4 and 7 respectively, then the eighth number is 3
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- 20
- 25
- 21.6
- 25.3
- 20
Correct Option: B
The average of eight numbers = 20
Sum of the eight numbers = 20 × 8 = 160
The average of first two numbers = 31
Sum of the first two numbers = 31
| The average of the next three numbers = | 64 | |
| 3 |
| Sum of the next three numbers = | 64 | × 3 = 64 |
| 3 |
Let the sixth number = n
∴ Seventh number = n + 4
and eighth number = n + 7
According to question ,
∴ 31 + 64 + n + n + 4 + n + 7 = 160
⇒ 3n + 106 = 160
⇒ 3n = 160 – 106 = 54
⇒ n = 54 ÷ 3 = 18
∴ Eighth number = n + 7 = 18 + 7 = 25
