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neokeynesian
10-24-2004, 04:16 AM
Result on a history test

Class ------No.of students taking test---- Average score

X--------------------54---------------------------70

Y--------------------41---------------------------73

Z--------------------32---------------------------76

Question:

The average score for all the students in the 3 classes is

a) less than 70 b)between 70 & 73 c)exactly 73

d) between 73 & 76 e) greater than 76

spiderman
10-24-2004, 05:37 AM
think of it this way.

73 is the mean.

there are 54 people who are trying to pull this mean down by 3. and there are 32 people who are trying to pull this mean up by 3.
so, which way will the mean go ? towards 54 right ?

hence B.

lmtuan
10-24-2004, 05:54 AM
The average score for all the students in the 3 classes is

(54*70 + 41*73 + 32*76)/(54 + 41 + 32) = 9205/127 ~~ 72.48

Thus, the answer of this question is B (between 70 & 73)

ajaymcc
10-24-2004, 01:41 PM
The average score for all the students in the 3 classes is

(54*70 + 41*73 + 32*76)/(54 + 41 + 32) = 9205/127 ~~ 72.48

Thus, the answer of this question is B (between 70 & 73)