set24-Q.4--B&W,Colour TV

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prachich1987: Legendary Member; Posts: 752; Joined: Sun Sep 12, 2010 2:47 am; Thanked: 20 times; Followed by:10 members; GMAT Score:700

set24-Q.4--B&W,Colour TV

by prachich1987 » Tue Dec 14, 2010 10:25 pm

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A shipment of 8 television sets contains 2 black-and-white sets and 6color sets. If 2 television sets are to be chosen at random from this shipment, what is the probability that at least 1 of the 2 sets chosen will be a black-and-white set?

A. 1/7 B. Â¼ C. 5/14 D. 11/28 E. 13/26

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Source: Beat The GMAT — Problem Solving | Tue Dec 14, 2010 10:25 pm

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Rahul@gurome: GMAT Instructor; Posts: 1179; Joined: Sun Apr 11, 2010 9:07 pm; Location: Milpitas, CA; Thanked: 447 times; Followed by:88 members

by Rahul@gurome » Tue Dec 14, 2010 10:49 pm

Required probability is = 1 - (probability that both sets are color sets).
Probability that both are color sets is 6C2/8C2 = 30/56 = 15/28.
So correct answer is 1 - 15/28 = 13/28.

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Sun Jun 02, 2019 4:10 pm

prachich1987 wrote:A shipment of 8 television sets contains 2 black-and-white sets and 6color sets. If 2 television sets are to be chosen at random from this shipment, what is the probability that at least 1 of the 2 sets chosen will be a black-and-white set?

A. 1/7 B. Â¼ C. 5/14 D. 11/28 E. 13/26

We can use the formula:

P(at least one black and white TV) = 1 - P(No black and white TV)

P(No black and white TV) = 6/8 x 5/7 = 3/4 x 5/7 = 15/28

P(at least one black and white TV) = 1 - 15/28 = 13/28

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