Average of x observation is 30, average of x other
observations is 33 and average of remaining x observations is 42. Average of all the observations is
A. 34 B. 35 C. 36 D. Cannot be deter-
mined E. None of these
Please give me a detailed solution as I am getting 35 as answer but the right answer is D according to the answer key.

sum of first x observations 3Ox similarly sum of other x observations is 33x and 42x
average=(30x+33x+42x)/3x
on solving u will get 35 as the answer hence b is the answer

i think 35 is right 

Total of first $$x$$ observations => 30$$x$$

Total of second $$x$$ observations => 33$$x$$

Total of third $$x$$ observations => 42$$x$$

Number of Observations => ( $$x$$ + $$x$$ + $$x$$ ) = 3$$x$$

Average of all Observations => $$\frac{30$$x$$+33$$x$$+42$$x$$}{3$$x$$}$$ = $$\frac{105}{3}$$ = $$35$$

Please check whether the key is correct

Cheers!! :)