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MathRevolution
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 20 Jun 2016, 17:48
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

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5% (low)

Question Stats:

87% (00:44) correct 13% (01:20) wrong based on 150 sessions

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In a store 6 different CDs are there. If John can buy 2 CDs, how many cases that he can buy are there?
A. 12
B. 15
C. 18
D. 21
E. 24

*An answer will be posted in 2 days.
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B
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 20 Jun 2016, 19:13
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Answer is 15:

This is a combinations problem, 6C2, which is 6!/(2!*4!) = 15.
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 22 Jun 2016, 20:38
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6C2=(6*5)/2!=15. Hence, the correct answer is B.
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 15 Oct 2016, 13:53
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In a very simple language the question is 'In how many ways can jack select 2CD's out of 6 different CD's
this can be done in 6C2 ways = \(\frac{6!}{4!2!}\) = 15

Correct answer - B
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 15 Oct 2016, 14:24
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rhine29388
In a very simple language the question is 'In how many ways can jack select 2CD's out of 6 different CD's
this can be done in 6C2 ways = \(\frac{6!}{4!2!}\) = 15

Correct answer - B
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Yeah you are absolutely correct it asks the ways to select... Consider this part :

Quote:
In a store 6 different CDs are there. If John can buy 2 CDs,how many cases that he can buy are there?
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Answer must be (B)
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Schools: IIM (A) ISB '24
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 15 Oct 2016, 22:14
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MathRevolution
In a store 6 different CDs are there. If John can buy 2 CDs, how many cases that he can buy are there?
A. 12
B. 15
C. 18
D. 21
E. 24

*An answer will be posted in 2 days.
Show more

METHOD - 1:
Make cases manually.
Let CDs are A, B, C, D, E, F
He may choose any pair as mentioned below
AB, AC, AD, AE, AF = 5 cases
BC, BD, BE, BF = 4 cases
CD, CE, CF = 3 cases
DE, DF = 2 cases
EF = 1 case
Total cases = 5+4+3+2+1 = 15

I hope people can observe the pattern in no. of cases found

Answer: Option B

METHOD - 2:
Total ways of making pairs = 6C2 = 15

Answer: Option B
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 03 May 2017, 19:16
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Bunuel: Please UnTag Probability
MathRevolution
In a store 6 different CDs are there. If John can buy 2 CDs, how many cases that he can buy are there?
A. 12
B. 15
C. 18
D. 21
E. 24

*An answer will be posted in 2 days.
Show more
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Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 03 May 2017, 22:34
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BrushMyQuant
Bunuel: Please UnTag Probability
MathRevolution
In a store 6 different CDs are there. If John can buy 2 CDs, how many cases that he can buy are there?
A. 12
B. 15
C. 18
D. 21
E. 24

*An answer will be posted in 2 days.
Show more
____________________
Done.
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In a store 6 different CDs are there. If John can buy 2 CDs, how many 24 Oct 2020, 02:52
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