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A student was asked to find the arithmetic mean of the following 12 numbers :
3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and y
He found the mean to be 12. The value of y will be :
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- 3
- 7
- 17
- 31
- 3
Correct Option: B
As we know that ,
| Average or Mean = | |
| Total number of quantities |
| Mean = | |
| 12 |
According to question,
| 12 = | |
| 12 |
∴ 137 + y = 144
∴ y = 144 - 137 = 7
