SOLUTION: a bag contains eleven discs numbered 1 to 11. two discs are selected at random with replacement. what is the probability that the sum is even?

Question 379994: a bag contains eleven discs numbered 1 to 11. two discs are selected at random with replacement. what is the probability that the sum is even?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
a bag contains eleven discs numbered 1 to 11. two discs are selected at random with replacement. what is the probability that the sum is even?
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The sum will be even if it is not odd.
The only way you get an odd result is to add an even to an odd.
There are 5 even digits and 6 odd digits.
There are 5*6 = 30 odd sums.
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But there are a total of 11*10 = 110 sums
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So 110 - 30 = 80 must be the number of even sums.
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P(getting an even sum) = 80/110 = 8/11
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Cheers,
Stan H.
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