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Andrew is trying to organize his notes by subject with a color-coding
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13 Jul 2022, 07:48
13 Jul 2022, 07:48
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Andrew is trying to organize his notes by subject with a color-coding system. If he has 5 different colors to work with, and a code can consist of one or two colors, how many subjects can he organize with this system if the order of the colors doesn’t matter?
A. 5
B. 7
C. 10
D. 15
E. 25
A. 5
B. 7
C. 10
D. 15
E. 25
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Re: Andrew is trying to organize his notes by subject with a color-coding
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13 Jul 2022, 07:58
13 Jul 2022, 07:58
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Carcass wrote:
Andrew is trying to organize his notes by subject with a color-coding system. If he has 5 different colors to work with, and a code can consist of one or two colors, how many subjects can he organize with this system if the order of the colors doesn’t matter?
A. 5
B. 7
C. 10
D. 15
E. 25
A. 5
B. 7
C. 10
D. 15
E. 25
Codes consisting of 1 color
There are 5 colors to choose from, so there are 5 codes consisting of 1 color
Codes consisting of 2 colors
Since order doesn't matter (e.g., selecting blue then red is the same as selecting red then blue), we can use combinations.
We can select 2 colors from 5 colors in 5C2 ways (= 10 ways)
So there are 10 codes consisting of 2 colors
TOTAL = 5 + 10
= 15
Answer: C
gmatclubot
Re: Andrew is trying to organize his notes by subject with a color-coding [#permalink]
13 Jul 2022, 07:58
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