Percentile Related Problem.

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angel11: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Tue Mar 24, 2009 8:08 am

by angel11 » Fri Apr 03, 2009 4:09 am

Can someone please help me out with this percentile problem.

Amy's grade was the 90th percentile of the 80 grades for her class.Of the 100 grades from another class,10 were higher than Amy's,and the rest were lower.If no other grade was the same as Amy's grade,then Amy's grade was what percentile of the grades of the two classes combined?

1) 72nd
2) 80th
3) 81st
4) 85th
5) 92nd

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Source: Beat The GMAT — Problem Solving | Fri Apr 03, 2009 4:09 am

lilu: Master | Next Rank: 500 Posts; Posts: 148; Joined: Wed Dec 10, 2008 5:13 pm; Location: SF, CA; Thanked: 12 times

by lilu » Fri Apr 03, 2009 3:50 pm

90th percentile out of 80 means that there were 8 more grades that were higher than Amy's
And there were 19 higher than Amy's grade out of 100
The total amount of people=100+80=180
The total amount of people with grades higher than Amy's=19+8=27
So, 153/180=85th percentile

D

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angel11: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Tue Mar 24, 2009 8:08 am

by angel11 » Fri Apr 03, 2009 10:49 pm

Thanks a lot Lilu....

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cbrombe1: Newbie | Next Rank: 10 Posts; Posts: 7; Joined: Thu Aug 21, 2008 8:17 am

by cbrombe1 » Tue Apr 14, 2009 10:54 am

I understand where you're getting the 8 from (.1 * 80)...can you please explain the logic behind 19?

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VP_Jim: GMAT Instructor; Posts: 1223; Joined: Thu May 01, 2008 3:29 pmFollowed by: 15 members; Location: Los Angeles, CA; Thanked: 185 times

by VP_Jim » Tue Apr 14, 2009 11:11 am

It's supposed to say that 19 were higher than Amy's - not 10.

Just a typo.

Jim S. | GMAT Instructor | Veritas Prep

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lgon: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Tue Oct 07, 2008 10:44 pm; Location: Chennai

by lgon » Tue Apr 21, 2009 5:54 am

VP_Jim wrote:It's supposed to say that 19 were higher than Amy's - not 10.

Just a typo.

Thanks! I was just thinking..that my answer(10+8)--> 162/180--> 90% ) 90% is not in the answer. Thanks Jim.

battle does not decide the outcome of war!

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