Committee X and Committee Y , which have no common members, will combine to form Committee Z . Does Committee X have more members than Committee Y ?

(1) The average (arithmetic mean) age of the members of Committee X is 25.7 years and the average age of the members of Committee Y is 29.3 years.

(2) The average (arithmetic mean) age of the members of Committee Z will be 26.6 years

general comment: in a WEIGHTED AVERAGE, if you have the 2 distances between the mean and each of the individual component averages, that's good enough to figure out the RATIO of the two components. here's how: distance between committee A and average = 29.3 - 26.6 = 2.7 distance between committee B and average = 26.6 - 25.7 = 0.9 ratio = 3:1

committee B must be bigger (because the average is closer to committee B's average), so the ratio of committee B : committee A is 3:1 (not 1:3). that's how it works. the same process applies to any other weighted average - good stuff.

WARNING: this procedure will NOT allow you to determine the actual SIZE of committee A or committee B, without any additional information; all it will give you is the RATIO of the two sizes. that's plenty sufficient to answer this problem, but, if the problem had asked for the NUMBER of members of any of the committees, the answer would be (e) as you had expected.