a car was driving at 66 km / h for 30 minutes , and then at 100 km / h for another 45 minutes . what was its average speed ?
"driving at 66 km / h for 30 minutes , distance covered = 60 * 1 / 2 = 30 km driving at 100 km / h for 45 minutes , distance covered = 100 * 3 / 4 = 75 km average speed = total distance / total time = 105 / 1.25 = 84 km / h answer : a"
divide(add(multiply(divide(30, add(30, 45)), 66), multiply(divide(45, add(30, 45)), 100)), divide(add(30, 45), const_60))