A basket contains 5 apples, of which 1 apple is spoiled and the rest are good. If you select 2 apples simultaneously and at random, what is the probability that the 2 apples will include the spoiled apple?
(A) 1/5 (B) 3/10 (C) 2/5 (D) 1/2 (E) 3/5
Answer: (C) 2/5
I chose (A) 1/5...and can't seem to understand why the answer would be (C).
Explanation, please? Thank you!
GMAT Forum
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- nk2120
- Guest
Perhaps not the fastest way to solve this, but it works fairly quickly nonetheless:
I lined up the apples and called them A,B,C,D,E, with A being the spoiled apple.
First, how many different combo's are there:
AB, AC, AD, AE
BC, BD, BE
CD, CE
DE
This tells me that there are 10 different combo's of choosing 2 apples simultaneously. Looking at the combo's with A in it, there are 4. Thus there are 4 out of 10 possible outcomes from choosing 2 apples with 1 as the spoiled apple. 4/10 reduces to 2/5, and thus the answer is C.
I lined up the apples and called them A,B,C,D,E, with A being the spoiled apple.
First, how many different combo's are there:
AB, AC, AD, AE
BC, BD, BE
CD, CE
DE
This tells me that there are 10 different combo's of choosing 2 apples simultaneously. Looking at the combo's with A in it, there are 4. Thus there are 4 out of 10 possible outcomes from choosing 2 apples with 1 as the spoiled apple. 4/10 reduces to 2/5, and thus the answer is C.
- RonPurewal
- Students
- Posts: 19744
- Joined: Tue Aug 14, 2007 8:23 am
big thread on this one already
http://www.manhattangmat.com/forums/post19455.html
http://www.manhattangmat.com/forums/post19455.html
3 posts Page 1 of 1