Question 653608
How many green blocks should be added to a bag that holds 1 blue block and 3 yellow blocks to make the probability of randomly selecting a green block from the bag equal to 1/2?
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Let the number  be "x":
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Equation:
x/(1+3+x) = 1/2
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x/(x+4) = 1/2
2x = x+4
x = 4 (# of green blocks to add)
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Cheers,
Stan H.