A university class is composed of $x$ men and $y$ women.

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swerve: Legendary Member; Posts: 2604; Joined: Sun Oct 29, 2017 2:04 pmFollowed by: 6 members

by swerve » Tue Sep 10, 2019 3:00 am

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A university class is composed of $x$ men and $y$ women. If 2 men and 13 women join the class, and one person is selected at random from the enlarged class, then the probability that a male is selected can be represented by

A. $\frac{x}{y}$
B. $\frac{x}{x+y}$
C. $\frac{x+2}{y+13}$
D. $\frac{x+2}{x+y+13}$
E. $\frac{x+2}{x+y+15}$

The OA is E

Source: Economist GMAT

Source: Beat The GMAT — Problem Solving | Tue Sep 10, 2019 3:00 am

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16206; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Tue Sep 10, 2019 5:24 am

swerve wrote:A university class is composed of $x$ men and $y$ women. If 2 men and 13 women join the class, and one person is selected at random from the enlarged class, then the probability that a male is selected can be represented by

A. $\frac{x}{y}$
B. $\frac{x}{x+y}$
C. $\frac{x+2}{y+13}$
D. $\frac{x+2}{x+y+13}$
E. $\frac{x+2}{x+y+15}$

The OA is E

Source: Economist GMAT

If 2 men join the class, then the total number of men = x+2
If 13 women join the class, then the total number of women = y+13
To, the TOTAL number of students = (x+2) + (y+13) = x + y + 15

P(male is selected) = (x+2)/(x + y + 15)

Answer: E

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

ELatour: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Fri Oct 28, 2016 6:59 am

by ELatour » Thu Sep 12, 2019 9:59 am

The easiest solution is to assume that both x and y are 0. If 2 men and 13 women join the class, then the chance that a man will be chosen is 2/15.

Which answer choice gives you that?

Not A
Not B
Not C
Not D
But E (0+2 / 0+0+15) does.

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8246; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Tue Sep 17, 2019 8:40 am

swerve wrote:A university class is composed of $x$ men and $y$ women. If 2 men and 13 women join the class, and one person is selected at random from the enlarged class, then the probability that a male is selected can be represented by

A. $\frac{x}{y}$
B. $\frac{x}{x+y}$
C. $\frac{x+2}{y+13}$
D. $\frac{x+2}{x+y+13}$
E. $\frac{x+2}{x+y+15}$

The OA is E

Source: Economist GMAT

We are given that a university class is composed of x men and y women and that 2 men and 13 women join the class.

The number of men in the enlarged class is x + 2, and the total number of students in the enlarged class is x + y + 2 + 13.

Thus, the probability of selecting a man from the enlarged class is:

(x + 2)/(x + y + 15)

Answer: E

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