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An ordinary 6-sided die has a number on each face from 1 to 6 (each number appears on one face). How many ways can I paint two faces of a die red, so that the numbers on the red faces don't add up to 7?

 Jun 7, 2018
 #1
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We have  C(6,2)   = 15 possibilites

 

They are

1,2      2,3      3,4    4,5    5,6

1,3      2,4      3,5    4,6

1,4      2,5      3,6

1,5      2,6

1,6

 

Only   1,6     2,5    and   3,4     add to  7

 

So....there are 12 ways to paint the faces so  that the numbers do not add to 7

 

 

cool cool cool

 Jun 7, 2018
 #2
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I see. Thanks!

Guest Jun 7, 2018

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