A bag contains 15 wool scarves, exactly one of which is red and exactly one of which is green. If Deborah reaches in and

This topic has expert replies
Moderator
Posts: 7187
Joined: Thu Sep 07, 2017 4:43 pm
Followed by:23 members
A bag contains 15 wool scarves, exactly one of which is red and exactly one of which is green. If Deborah reaches in and draws three scarves, simultaneously and at random, what is the probability that she selects the red scarf but not the green scarf?

a) 2/35
b) 1/15
c) 6/35
d) 13/70
e) 1/5



OA C

Source: Veritas Prep
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3008
Joined: Mon Aug 22, 2016 6:19 am
Location: Grand Central / New York
Thanked: 470 times
Followed by:34 members
BTGmoderatorDC wrote:
Fri Jan 31, 2020 4:40 pm
A bag contains 15 wool scarves, exactly one of which is red and exactly one of which is green. If Deborah reaches in and draws three scarves, simultaneously and at random, what is the probability that she selects the red scarf but not the green scarf?

a) 2/35
b) 1/15
c) 6/35
d) 13/70
e) 1/5

OA C

Source: Veritas Prep
Probability that she selects the red scarf but not the green scarf is given by

(# of ways to select 1 red and 2 out of 13 scarves) / (# of ways to select 3 out of 15 scarves)

= (1C1*13C1) / (15C3) = [(13.12)/(1.2)] / [(15.14.13)/(1.2.3)] = 6/35

The correct answer: C

Hope this helps!

-Jay
_________________
Manhattan Review

Locations: Manhattan Review Madhapur | GMAT Prep Kukatpally | GRE Prep Jayanagar | Tarnaka GRE Coaching | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.