Hi All,
Weighted Average questions can be solved in a variety of ways - Algebraically, Tactically or Conceptually. Here's a conceptual approach to this question...
We're given a few facts to work with:
1) The average of all scores on a certain algebra test was 90.
2) The average of the 8 male students’ grades was 87
3) The average of the female students’ grades was 92
We're asked how many female students took the Test.
For the sake of ease, we can assume that each male scored 87 on the Test. Since the average score was 90, each of those 'male scores' brought the average DOWN by 3 points....
90 - 87 = 3
Since there were 8 males, that is a total of (8)(3) = 24 points that have to be 'made up for' by the female scores.
If we assume that each female scored 92, then each of those individual scores 'makes up for' 2 of the points....
92 - 90 = 2
We need an answer that will counter the 24 points that we 'dropped'...
24/2 = 12 female test takers needed
Final Answer:
GMAT assassins aren't born, they're made,
Rich