How many of the girls in a group of 200 children have an average score

Question

How many of the girls in a group of 200 children have an average score of 80 in their final exams?

(1) 45% of the children have an average score of 80 in their final exams.
(2) 50% of the children in the group are girls.

14101992 · Answer

Statement 1: Insufficient. We do not know the number of girls.
Statement 2: Insufficient. We can just find that there are 100 number of girls.
Combining 1 and 2,
We still do not know whether all 45% student who got an average of 80 are girls or 40% or 20% or 0%. 
Hence, Answer will be E.

OptimusPrepJanielle · Answer

Total children = 200

Statement 1: 45% of the children have an average score of 80 in their final exams
Hence 90 children have an average score of 80.
We do not have any information about the score of the girls.
INSUFFICIENT

Statement 2: 50% of the children in the group are girls
Hence, 100 children are girls.
Still no information about the scores.
INSUFFICIENT

Combining both statements: 
90 have average score of 80
Total 100 are girls.

But we still have no information about the number of girls out of the children who have average score of 80.
INSUFFICIENT

Correct Option: E

Nightfury14 · Answer

Statement 1) Does not specify anything about the girls .. Insufficient.
Statement 2) Does not specify anything about the scores .. Insufficient.

Statement 1) & 2) The statements combined due not give any details about the score of the girls in the group .. Insuffient.

Choice E) is the correct Ans.

Good luck
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adiagr · Answer

Girls avg.JPG It may be seen that from Statement 1, we do not get the exact breakup. So it is not sufficient Similarly from Statement 1, we do not get the exact breakup. So it is not sufficient Even after combining the two, we will not be able to get the unknown desired. hence answer is E

MarkGMATMentor · Answer

This is a good example of a DS question that, while not mathematically difficult, can still trap you if you're not careful. Make sure that only one answer is possible before you decide that a statement or statements are sufficient.

Statement 1: 
This tells us how many children in the group have an average score of 80 in their final exams (45% of 200 is 90), but not how many of those 90 children are girls. It could be all of them or it could be half of them, for example.  Insufficient.

Statement 2: 
This tells us that half the children are girls (50% of 200 is 100), but doesn't tell us how many of them got a score of 80 in their final exams. It could be none of the girls or all of the girls, for example.  Insufficient.

Together: 
The two statements seem to complement each other well: the first statement gives you the percentage that got an 80 average, and the second statement tells you how many of the children are girls. It may seem that the answer is C.

But when the statements fit together so easily,  be skeptical.  You need to make sure that only one answer is possible.

Here, note that both the 45% and the 50% refer to the entire group, not the sub-group we care about.  For example, maybe the 50-50 gender split  does not apply  to the 90 children who got an average score of 80, and all of those 90 children are girls. Or maybe none of them are. Or maybe the 50-50 gender split  does   apply  to the 90 children who got an average score of 80, so 45 girls and 45 boys got an average score of 80.

Any of these scenarios are possible (as are many others), so the statements together are  insufficient.   The answer is E.

Watch out for the C Trap: when the two statements seem to complement each other well, be skeptical. Test whether you can get more than one answer, in which case the answer is E.  (Also important on some questions: make sure that you need  both  statements in order to get only one answer.)

How many of the girls in a group of 200 children have an average score

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GMAT Data Sufficiency (DS) Questions

How many of the girls in a group of 200 children have an average score

Prep Toolkit

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