word problem

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armaan700+: Senior | Next Rank: 100 Posts; Posts: 75; Joined: Sun Jun 14, 2009 1:41 am; Location: india; Thanked: 2 times; Followed by:1 members

by armaan700+ » Sat Jan 30, 2010 10:48 pm

word problem is stumbling me

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Source: Beat The GMAT — Problem Solving | Sat Jan 30, 2010 10:48 pm

thephoenix: Legendary Member; Posts: 1560; Joined: Tue Nov 17, 2009 2:38 am; Thanked: 137 times; Followed by:5 members

by thephoenix » Sat Jan 30, 2010 10:53 pm

Mean = 21 hours
SD = 6
One or Two SD below mean is

Mean - 1 ( SD ) = 21 -6 = 15
Mean - 2 ( SD) = 21 - 12 = 9

9 < n < 15

Ans n =12

ajith: Legendary Member; Posts: 1275; Joined: Thu Sep 21, 2006 11:13 pm; Location: Arabian Sea; Thanked: 125 times; Followed by:2 members

by ajith » Sat Jan 30, 2010 11:40 pm

armaan700+ wrote:word problem is stumbling me

The answer is 1-2 SD below the mean
Mean =12 SD = 6
=> Answer is between 9 and 15 .. only one choice is between 9 and 15

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