GMAT prep : probability
This topic has expert replies
A basket contains 5 apples of which 1 is spoiled and the rest are good. If Henry is to select 2 apples from teh basket simultaneously and at random, what is the probability that the 2 apples selected will include the spoiled apple?
- givemeanid
- Master | Next Rank: 500 Posts
- Posts: 277
- Joined: Sun Jun 17, 2007 2:51 pm
- Location: New York, NY
- Thanked: 6 times
- Followed by:1 members
- jayhawk2001
- Community Manager
- Posts: 789
- Joined: Sun Jan 28, 2007 3:51 pm
- Location: Silicon valley, California
- Thanked: 30 times
- Followed by:1 members
sneakpeak, can you please post the answer choices along with the
question.
Number of ways in which you can get 1 spoiled apple = 1 * 4C1 = 4
Number of ways to choose 2 apples from a set of 5 = 5C2 = 10
So, probability will be 4/10 = 2/5
question.
Number of ways in which you can get 1 spoiled apple = 1 * 4C1 = 4
Number of ways to choose 2 apples from a set of 5 = 5C2 = 10
So, probability will be 4/10 = 2/5
Another way to tackle this is the opposite or complement of the probability of chosing 1 bad apple out of two is figuring out the probability of choosing no bad apples and subtracting that from one.
Probability of choosing one good apple....4/5
Probability of choosing second good apple....3/4
4/5 * 3/4 = 12/20
1 - 12/20 = 20/20 - 12/20 = 8/20 = 2/5
Probability of choosing one good apple....4/5
Probability of choosing second good apple....3/4
4/5 * 3/4 = 12/20
1 - 12/20 = 20/20 - 12/20 = 8/20 = 2/5