You can put this solution on YOUR website! A box contains 5 red and 7 green balls. How many ways can 2 balls be selected with the 2 balls the same color??
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Selecting 2 reds or selecting 2 greens mutually exclusive events.
Formula: P(A or B) = P(A)+P(B)
P(2red) = [number of ways to select 2 from 5]/[# of ways to select 2 from 12]
P(2green)=[# of ways to select 2 from 7]/[# of ways to select 2 from 12}
P(2 balls same) = P(2red)+P(2green)
=[5C2]/[12C2] + [7C2]/[12C2]
=(10+21)/66
=31/66
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Cheers,
Stan H.
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