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 ?
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 = 30 seconds . answer a
divide(add(divide(divide(400, divide(multiply(7.2, const_1000), const_3600)), const_2), divide(400, divide(multiply(7.2, const_1000), const_3600))), const_10)