In Spring the pool is open from 8 am to 7 pm. How many hours is the pool open each day in the Spring?

• A. 9 hours
• B. 11 hours
• C. 10 hours
• D. 12 hours

Answer: (B)

The duration is found by subtracting the start time from the end time. From 8 am to 7 pm is the same as 8 to 19 in 24-hour terms, and 19 − 8 equals 11 hours. You can also see it by splitting the day: 8 am to noon is 4 hours, then noon to 7 pm is 7 hours, for a total of 11 hours. So the pool is open for 11 hours. The other totals would require ending earlier or later than 7 pm (for example, 9 hours would end at 5 pm, 10 hours at 6 pm, and 12 hours at 8 pm).