a river boat leaves silver town and travels upstream to gold town at an average speed of 6 kilometers per hour . it returns by the same route at an average speed of 8 kilometers per hour . what is the average speed for the round - trip in kilometers per hour ?
"pick a number which is lcm of 8 and 6 = 24 . upstream time = 24 / 6 = 4 hrs downstream time = 24 / 8 = 3 hrs total time = 7 hrs total distance = 48 average speed = 48 / 7 = 6.8 km / hr"
divide(multiply(multiply(6, 8), const_2), add(6, 8))