Question 1135102

Commuter trains leaves every 20 minutes from 6 am through 9am and every 30 minutes until 9 pm. How many trains leave the station from 6 am through 4pm?
<pre>Number from 6:00 a.m. - 8:40 a.m., inclusive: 9
Number from 9:00 a.m. - 4:00 p.m., inclusive: 15
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