A zoo sold admission tickets to groups of 30 people every 5 minutes

In each hour, for example, the 9am hour-period (i.e., 9:00 am to 9:59 am), the first time tickets were sold is at 9:00 am and the last time tickets were sold is at 9:55 am. Therefore, tickets were sold for (55 - 0)/5 + 1 = 12 times. Therefore, 12 x 30 = 360 tickets were sold during that hour. Similarly, 360 tickets were sold during the 1-hour period of 10am, 11am, 12pm, 1pm, 2pm, 3pm, 4pm and 5pm. (Notice that we don’t exactly have a full hour during the 5pm hour-period; however, it doesn’t change the fact that 12 times the tickets were sold during the 5pm period since the first time tickets were sold during that period is at 5:00 pm and the last time is at 5:55pm.) Since we have 9 one-hour periods and during each one-hour period 360 tickets were sold, a total of 9 x 360 = 3240 tickets were sold.

Answer: E