At peak hours, 11 am - 1 pm and 5 pm - 6 pm, the local fast-food restaurant serves 12 cars every 15 minutes. Off-peak times, they serve 8 cars every 15 minutes. From 4 pm - 6 pm, how many customers do they serve? Let's be accurate as possible.
5 pm - 6 pm is one hour and they measure service in 15 - minute blocks so 60 / 15 = 4 15 min blocks. At peak times, they serve 12 cars every 15 minutes so they serve 12 * 4 = 48 cars in 60 minutes. Off peak times, 4pm - 5 pm, they serve 8 cars every 15 minutes so they serve 8 * 4 = 32 cars in 60 minutes. From 4pm - 5 pm they serve 32 cars and from 5pm - 6 pm they serve 48 cars so they serve 32 + 48 = 80 cars.
The answer: 80.