Question

Of 2,000 students surveyed, 80% indicated that they commute to school each day. of those that commute to school each day, 83% spend more than $25 a week on gasoline. of those that do not commute to school each day, 95% indicated that they do not spend more than $25 a week on gasoline. a student surveyed is chosen at random. 4. what is the probability that this student does spend more than $25 a week on gas, given that he/she does commute to school each day?

Answer 1

Commute to school 
= 80% of 2000
= 0.8 x 2000
= 1600

Commute to school and spend more than $25 on gasoline
= 83% of 1600
= 0.83 x 1600
= 1328

Given that he/she commute to school,
P(Spend more than $25) = 1382/1600 = 691/800

Answer: 691/800