SOLUTION: Please solve this question: The ratio of boys to girls in Mr.Peter class is 3:4. On the last exam, 3/4 of the boys passed the exam and 4/5 of the girls passed. If a students exam

Question 421181: Please solve this question:
The ratio of boys to girls in Mr.Peter class is 3:4. On the last exam, 3/4 of the boys passed the exam and 4/5 of the girls passed. If a students exam paper is chosen at random, what is the probability that it has a passing grade?
also
How to do it on TI-84
Thanks
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The ratio of boys to girls in Mr.Peter class is 3:4.
# of boys = 3x
# of girls = 4x
Total # of boys and girls = 7x
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On the last exam, 3/4 of the boys passed the exam and 4/5 of the girls passed.
(3/4)(3x) = (9/4)x boys passed
(4/5)(4x) = (16/5)x girls passed
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If a students exam paper is chosen at random, what is the probability that it has a passing grade?
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Total number who passed = [(9/4)+(16/5)]x = (45+56)/20 = (101/20)x
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P(passed) = [101/20]x/7x = 101/140 = 0.7214
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Cheers,
Stan H.
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