Question

Average of five numbers is 61. If the average of first and third number is 69 and the average of second and fourth number is 69 what is the fifth number ?
A. 31
B. 29
C. 25
D. 35

Answer 1

Correct Answer - B
Let the five no. be `x_(1),x_(2),x_(3),x_(4),x_(5)`
Average of 5 numbers =61
`(x_(1)+x_(2)+x_(3)+x_(4)+x_(5))/(5)=61`
`x_(1)+x_(2)+x_(3)+x_(4)+x_(5)=305`
Now, `(x_(1)+x_(2))/(2)=69`
`x_(1)+x_(3)=138`
`(x_(2)+x_(4))/(2)=69`
`x_(2)+x_(4)=138`
Now , `x_(1)+x_(3)+x_(2)+x_(4)+x_(5)=305`
`138+138+x_(5)=305`
`x_(5)=305-276`
`x_(5)=29`