winson traveled the entire 60 miles trip . if he did the first 10 miles of at a constant rate 20 miles per hour and the remaining trip of at a constant rate 48 miles per hour , what is the his average speed , in miles per hour ?
average speed = sum of distance / sum of time . if he travelled the first 10 miles at 20 miles / hr , it would take 0.5 hr . for the remaining trip , if he went at 48 miles / 1 hr , it would take 1 hour . then , the average speed is 60 miles / ( 0.5 + 1 ) hrs = 40 miles / 1 hr . therefore , the answer is e .
divide(60, add(divide(subtract(60, 10), 48), divide(10, 20)))