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Percentile

by Akansha » Sun May 29, 2011 10:32 am
Angela's grade was in the 90th percentile out of 80 grades in her class. In
another class there were 19 grades higher than Angela's. If nobody had Angela's
grade, then Angela was what percentile of the two classes combined?
a. 72
b. 80
c. 81
d. 85
e. 92

OA is D

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by gmatmachoman » Sun May 29, 2011 10:56 am
{90 * 80 + 81 *100} / (90 +100)

= 85

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by [email protected] » Sun May 29, 2011 7:36 pm
Akansha wrote:Angela's grade was in the 90th percentile out of 80 grades in her class. In
another class there were 19 grades higher than Angela's. If nobody had Angela's
grade, then Angela was what percentile of the two classes combined?
a. 72
b. 80
c. 81
d. 85
e. 92

OA is D

The question has missed something.
It should be that "In another class of 100 students, there were 19 grades higher than Angela's."
Solution:
Since Angela's grade was in the 90th percentile out of 80 grades in her class, 90% * 80 = 72 students had grades less than her.
In another class of 100, if 19 had more than her, 100- 19 = 81 had less than her. Note that nobody had grade that was equal to Angela's.
So, in total, out of 80+100 = 180 grades, 72+81 = 153 grades were less than Angela's grade.
Or Angela's percentile was 153/180*100 = 85% of the two classes combined.

The correct answer is d.
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