A cyclist climbs a hill with a length of 400 m with a speed of 7.2 km/h. When descending, the speed is two times greater. How much time is necessary for the cyclist to climb and descend the hill?  Select:
A) 30 seconds B) 20 seconds C) 40 seconds D) 10 seconds E) None
7.2 km = 7200 m. 1 h = 3600 s. The speed will be 7200 m/3600 s = 2 m/s. The necessary time to climb will be 20 seconds. When descending, if the speed is two times greater, the necessary time will be two times smaller, so 10 seconds. The total necessary time is 20 s + 10 s  7200  /3600= 
<gadget id="calculator"> 7200  /3600</gadget>
<output>2</output>
2 m/s. The necessary time to climb will be 20 seconds. When descending, if the speed is two times greater, the necessary time will be two times smaller, so 10 seconds. The total necessary time is 20 s + 10 s= 30 seconds.   30 secondsnswer 30 seconds
<result>A</result>
A cyclist climbs a hill with a length of 400 m with a speed of 7.2 km/h. When descending, the speed is two times greater. How much time is necessary for the cyclist to climb and descend the hill?