SOLUTION: You select at random 2 numbers from 1 to 8. What is the probability that the sum of two numbers selected is 3? Answer should be as a common fraction.

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Question 388907: You select at random 2 numbers from 1 to 8. What is the probability that the sum of two numbers selected is 3? Answer should be as a common fraction.
Found 2 solutions by edjones, jrfrunner:
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
1 and 2 are the only numbers in the group whose sum is 3.
nCr=combination of n things taken r at a time=n!/((n-r)!*r!)
=8!/(6!*2!)=28
1/28
.
Ed

Answer by jrfrunner(365) About Me  (Show Source):
You can put this solution on YOUR website!
The answer depends on whether you are selecting with replacement of the selected numbers or without replacement of the selected numbers.
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In order for the two numbers to sum to 3, the numbers selected must be 1 and 2.
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Without replacement:
Probability of selecting 1 and 2=P(1,2)+P(2,1)=1/8*(1/7)+1/8*(1/7)=2/56=1/28
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with replacement:
P(1,2)+P(2,1)=1/8*(1/8)+1/8*(1/8)=2/64=1/32