If the mean of the observation `x, x+3, x+5, x+7` and `x+10` is `9`, then mean of the last three observations is

Options

A. `10(1)/(3)`
B. `10(2)/(3)`
C. `11(1)/(3)`
D. `11(2)/(3)`

Answer

C

Explanation

Mean = 9
`rArr (x+x+3+x+5+x+7+x+10)/(5) = 9`
`rArr 5x+25 = 45`
`rArr x = 4`
Last three observations are 4+5, 4+7, 4+10 i.e., 9,11,14
` "Mean"= (9+11+14)/(3) = (34)/(3) = 11(1)/(3)`
Hence, (c) is the correct answer.