a car was driving at 80 km / h for 40 minutes , and then at 60 km / h for another 40 minutes . what was its average speed ?
"driving at 80 km / h for 40 minutes , distance covered = 80 * 2 / 3 = 53.33 km driving at 90 km / h for 40 minutes , distance covered = 90 * 2 / 3 = 60 km average speed = total distance / total time = 113.33 / 1 = 113.33 km / h answer : 113.33 km / h"
divide(add(multiply(divide(40, add(40, 40)), 80), multiply(divide(40, add(40, 40)), 60)), divide(add(40, 40), const_60))