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The average of first three numbers is double of the fourth number. If the average of all the four numbers is 12, find the 4th number.
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- 16
- 48/7
- 20
- 18/7
- 16
Correct Option: B
Given , The average of first three numbers is double of the fourth number .
| ⇒ | = 2d | |
| 3 |
⇒ a + b + c = 6d ...(i)
According to question ,
| Also, | = 12 | |
| 4 |
⇒ a + b + c + d = 48
⇒ 6d + d = 48 { From (i) }
⇒ 7d = 48
| ⇒ d = | ||
| 7 |
