rnaah wrote:A student scored the 90th percentile out of 80 grades in her class. In another class with 100 grades, 19 are above her grade. If no other grade is equal to her own, what is her average percentile from the two classes?
Shankar's solution is great.
Another approach:
In the class with 80 grades, the student = 90th percentile.
In the class with 100 grades, the student = 81st percentile. (Since 19 grades are higher, implying that 81 grades are lower.)
Thus, to determine the weighted average of the 180 grades:
[(80*90)+(100*81)] / 180 = 15300/180 = 85.
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