a car was driving at 50 km / h for 30 minutes , and then at 40 km / h for another 30 minutes . what was its average speed ?
"driving at 50 km / h for 30 minutes , distance covered = 50 * 1 / 2 = 25 km driving at 40 km / h for 30 minutes , distance covered = 40 * 1 / 2 = 20 km average speed = total distance / total time = 45 / 1 = 45 km / h answer : a"
divide(add(multiply(divide(30, add(30, 30)), 50), multiply(divide(30, add(30, 30)), 40)), divide(add(30, 30), const_60))