# SOLUTION: From a class of girls and boys, the probability that one student chosen at random will be a boy is 2/3. If 3 girls leave the class, the probability that a student chosen at random

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 Question 612870: From a class of girls and boys, the probability that one student chosen at random will be a boy is 2/3. If 3 girls leave the class, the probability that a student chosen at random will be a boy is 4/5. How many boys and girls are ther in the class before the 3 girls leave? Thanks !Answer by stanbon(57344)   (Show Source): You can put this solution on YOUR website!From a class of girls and boys, the probability that one student chosen at random will be a boy is 2/3. If 3 girls leave the class, the probability that a student chosen at random will be a boy is 4/5. How many boys and girls are ther in the class before the 3 girls leave? -------------------------- P(b) = 2/3 b/(b+g) = 2/3 3b = 2b+2g b = (2/3)b + (2/3)g (1/3)b = (2/3)g b = 2g ------------ Equation: b/(b + g-3) = 4/5 ------ (2g)/(2g + g-3) = 4/5 10g = 4(3g-3) 10g = 12g-12 2g = 12 g = 6 (original # of girls) ---- b = 2g = 12 (original # of boys) ==================================== Cheers, Stan H. ================