Damager wrote:

1) The average age of members of Committee X is 25.7 yrs and the ave age of the members of Committee Y is 29.3 yrs

(2) The ave age of the members of Committee Z will be 26.6 yrs

Assume x has m members and y has n members

Total Age of x = 25.7*m

Total Age of y = 29.3*n

Average age of Z will be (25.7*m+29.3*n)/(m+n) = 26.6 (****)

So u get 25.7* m + 29.3 * n = 26.6*m + 26.6*n

2.7n=.9m

m/n=2.7/.9=3 ==> m=3n

Although in this question if u reach (****) u can choose C as answer

This is very good to know in case we are faced with PS question and need to solve all the way through. For a DS as long as you know this basic concept you do not need to solve all the way and could approach this intuitively.

IF:

25.7+29.3/2 = 27.5 Which is > then the mean age of committee Z. So that means there must be more x members to bring the avg. age down.

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