Question

Students in a middle school must choose to take either band or chorus. in a given academic year, 60% of the pupils choose band and the rest choose chorus. 30% of the students who are taking band are girls, and 70% who are taking chorus are girls. if a student is randomly selected from this academic year, what is the probability that it is a boy?
a.0.46
b.0.49
c.0.50
d.0.54

Answer 1

60% choose band......40% choose chorus

30% who are taking band are girls......30% of 60% is (0.3 * 0.6) = 0.18 or 18%..so 18% are girls.
70% who take chorus are girls....70% of 40% is (0.7 * 0.4) = 0.28 or 28%...so 28% are girls.

18% + 28%  = 46%....so a total of 46% taking band and chorus are girls.....so that leaves (100% - 46%) = 54% ( or 0.54) are boys