Suppose that your school day is from 8:00 am until 3:00 pm. You eat lunch at 12:00 pm. If there is a fire drill at a random time during the day, what is the probability that it begins before lunch?

The correct answer is: 57%

From 8 am to 3 pm, total number of hours is 7.
Lunch is eaten at 12 pm. So before lunch means from 8 am to 12 pm which is 4 hours.
Probability =
= 0.571 = 57.1%

time at school before lunch = 12 - 8 = 4 hours
time at school after lunch = 3 pm - 12 noon = 3 hours.
total time at school = 4 + 3 = 7 hours.
probability of having drill before lunch = time before lunch / total time
= 4 / 7 = 0.5714
it can be expressed as a percentage by multiplying by 100
= 57.14 %