Interesting GMATFix Problem-36

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arora007: Community Manager; Posts: 1048; Joined: Mon Aug 17, 2009 3:26 amFollowed by: 27 members; Location: India; Thanked: 51 times; GMAT Score:670

by arora007 » Thu Sep 23, 2010 9:55 am

The test scores of 1050 students have a normal distribution. If the average test score is 73 and the standard deviation is 10.5, approximately how many students have a test score less than 62.5?
A)147
B)168
C)205
D)288
E)357

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Source: Beat The GMAT — Problem Solving | Thu Sep 23, 2010 9:55 am

sanabk: Master | Next Rank: 500 Posts; Posts: 174; Joined: Fri Apr 02, 2010 3:41 pmFollowed by: 1 member; Thanked: 6 times

by sanabk » Thu Sep 23, 2010 12:04 pm

From the attached image, one can say that 68% of the class received a score within 1 standard deviation of the mean (73). This leaves 32% of which 16% are below 1SD of mean (62.5) and 16% are above 1SD of mean (83.5).

The number of students with score less than 62.5 = 16%(1050)=168.
B

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arora007: Community Manager; Posts: 1048; Joined: Mon Aug 17, 2009 3:26 amFollowed by: 27 members; Location: India; Thanked: 51 times; GMAT Score:670

by arora007 » Fri Sep 24, 2010 1:11 am

sanabk wrote:

From the attached image, one can say that 68% of the class received a score within 1 standard deviation of the mean (73). This leaves 32% of which 16% are below 1SD of mean (62.5) and 16% are above 1SD of mean (83.5).

The number of students with score less than 62.5 = 16%(1050)=168.
B

Do we need to learn what u have given in this figure, 68%, 16% etc. ?

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sanju09: GMAT Instructor; Posts: 3650; Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members; Location: India; Thanked: 267 times; GMAT Score:760

by sanju09 » Fri Sep 24, 2010 1:15 am

arora007 wrote:
sanabk wrote:

From the attached image, one can say that 68% of the class received a score within 1 standard deviation of the mean (73). This leaves 32% of which 16% are below 1SD of mean (62.5) and 16% are above 1SD of mean (83.5).

The number of students with score less than 62.5 = 16%(1050)=168.
B
Do we need to learn what u have given in this figure, 68%, 16% etc. ?

Well, it's helpful if we really do, but the demonstration here is a treat to watch.

The mind is everything. What you think you become. -Lord Buddha

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The Princeton Review - Manya Abroad
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www.manyagroup.com

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