Compound Probabilities
- Thread starter Nori
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Harry_the_cat
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How many students are there in total?
HallsofIvy
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Given "x" students out of a total of "y" students do a particular thing the probability that a randomly chosen student does that thing is x/y.
For example, we know that 10+ 5= 15 students play a brass instrument and that there are 10+ 5+ 35+ 5= 55 students total. The probability that a randomly selected student plays a brass instrument is 15/55= 3/11. If we had been asked the probability that a randomly selected student plays only a brass instrument then the numerator would have been the "10" that play only a brass instrument, 10/55= 2/11.
You have already calculated that 50 students out of the 55 play either a string or brass instrument or both.
For example, we know that 10+ 5= 15 students play a brass instrument and that there are 10+ 5+ 35+ 5= 55 students total. The probability that a randomly selected student plays a brass instrument is 15/55= 3/11. If we had been asked the probability that a randomly selected student plays only a brass instrument then the numerator would have been the "10" that play only a brass instrument, 10/55= 2/11.
You have already calculated that 50 students out of the 55 play either a string or brass instrument or both.