Question

Choose the correct answer in each of the following questions:
If the mean of x, x + 3, x+5, x +7, x+ 10 is 9, the mean of the last three observations is
(a) $10\frac{1}{3}$
(b) $10\frac{2}{3}$
(c) $11\frac{1}{3}$
(d) $11\frac{2}{3}$

Answer 1

Mean of last three observation will be 11.33

ANSWER:
(c) 1113

Mean of 5 observations = 9
We know:
Mean=Sum of observationsTotal number of observations⇒9=(x+x+3+x+5+x+7+x+10)/5
⇒9=(5x+25)/5
⇒5x+25=45
⇒5x=20
⇒x=4Therefore, the last three observations are (4+5), (4+7) and (4+10), i.e., 9, 11 and 14.Now,Mean of the last three terms=(9+11+14)/3=1113