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The average of first three numbers is thrice the fourth number. If the average of all the four numbers is 5, then find the fourth number.
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- 4.5
- 5
- 2
- 4
- 4.5
Correct Option: C
Let the numbers be a, b, c.
According to question ,
| = 3d | ||
| 3 |
&trArr; a + b + c = 9d .........( 1 )
| Again, | = 5 | |
| 4 |
⇒ a + b + c + d = 20
⇒ 9d + d = 20 { ∴ from eq. ( 1 ) }
⇒ 10d = 20
⇒ d = 2
