Conditional probability
Compute conditional probability P(A | B) from a two-way survey summary. Unlimited questions, five difficulty levels, and a full worked solution every time — free.
Try one
A survey of 40 grade 12 students found that 21 play a school sport. Of those, 20 have a part-time job. Of the remaining 19 who don't play a school sport, 6 have a part-time job. If you randomly pick one of the students who play a school sport, what is the probability that they don't have a part-time job?
Answer: 1/21
See one solved, step by step
A survey of 60 students found that 27 take the school bus. Of those, 24 live more than 3 km from school. Of the remaining 33 who don't take the school bus, 21 live more than 3 km from school. If you randomly pick one of the students who take the school bus, what is the probability that they live more than 3 km from school?
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