60. The elevator in an eleven - storied office building travels at the rate of one floor per minute, which allows time for picking up and letting down passengers. At the main floor and at the top floor the operator stops for 1 minute. How many complete (return) trips will the operator makes during a 7 hour period?
উত্তর: খ) 60
- ক) 50
- খ) 60
- গ) 80
- ঘ) None
ব্যাখ্যা
B) 60. An eleven-storey building has 10 gaps between floors. At minute per floor, one way takes 2.5 minutes. A return trip is 2.5 minutes up, a 1-minute stop at the top, 2.5 minutes down and a 1-minute stop at the main floor: 7 minutes in all. Seven hours is 420 minutes, and 420 ÷ 7 = 60.
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