probability question

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anwarma: Senior | Next Rank: 100 Posts; Posts: 56; Joined: Sat May 24, 2008 5:18 pm; Thanked: 1 times

by anwarma » Wed Jun 11, 2008 3:14 pm

Sixty percent of the members of a study group are women, and 45 percent of those women are lawyers. If one member of the study group is to be selected at random, what is the probability that the member selected is a woman lawyer?

(A) 0.10
(B) 0.15
(C) 0.27
(D) 0.33
(E) 0.45

ANSWER is C

I am having trouble understanding the statement "If one member of the study group is to be selected at random, what is the probability that the member selected is a woman lawyer?" This is where I did not know what to do like how do I use the concept of probability, can someone help me?

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Source: Beat The GMAT — Problem Solving | Wed Jun 11, 2008 3:14 pm

babachal: Junior | Next Rank: 30 Posts; Posts: 28; Joined: Mon Jun 02, 2008 5:30 pm; Thanked: 3 times

by babachal » Wed Jun 11, 2008 3:30 pm

first we have to find how many percent of group are woman lawyers, if 60 percent of women and of those women 45 percent are lawyers, it is equal to 0.6*0.45=0.27. it means that 27% of the group are woman lawyers. to solve probabilty, randomly picked number and whole number are needed. 27 is randomly picked number and 100 is whole number. to find probability we have to divide 27 by 100 which is equal to 0.27.

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Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members; Location: Toronto; Thanked: 1710 times; GMAT Score:800

by Stuart@KaplanGMAT » Wed Jun 11, 2008 8:02 pm

babachal wrote:first we have to find how many percent of group are woman lawyers, if 60 percent of women and of those women 45 percent are lawyers, it is equal to 0.6*0.45=0.27. it means that 27% of the group are woman lawyers. to solve probabilty, randomly picked number and whole number are needed. 27 is randomly picked number and 100 is whole number. to find probability we have to divide 27 by 100 which is equal to 0.27.

Why a second step?

If 27% of the people are women lawyers, there's a 27% chance that the one picked is a woman lawyer.

Answers are in decimal form, so just convert 27% to .27.

(edited for grammar)

Last edited by Stuart@KaplanGMAT on Wed Jun 11, 2008 9:57 pm, edited 1 time in total.

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babachal: Junior | Next Rank: 30 Posts; Posts: 28; Joined: Mon Jun 02, 2008 5:30 pm; Thanked: 3 times

by babachal » Wed Jun 11, 2008 9:08 pm

the way you said is understandable for only who has well experience in probability, if some other terms added, the answerer would not find with the easy way, he might confuse!

anyway, thank you

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