During a particularly snowy day last winter, 25% of the flights departing from Vancouver International Airport were cancelled. Of the flights not cancelled, one-third were delayed because they had to be de-iced. If 150 flights departed on time and no flights left early,how many flights were originally scheduled to depart that day?

Solution:

The percent of flights which were originally scheduled to depart that day is

1-0.25-(1-0.25)*2/3 = 0.50

so 0.50*150 = 75

so 75 flights were originally scheduled to depart that day.