Question

A truck with a heavy load drove from Boston to New York at 50 mph. After dropping of the load, it returned from New York to Boston with a speed of 70 mph. What is the average speed of the truck for the whole trip?

Answer 1

Answer:

175/3 or 58.333...

Step-by-step explanation:

This is fairly complicated but I will try to make it as simple as possible. I also apologize in advance for how impossible it is to make fractions look like fractions. I also had to insert a bunch of unnecessary parentheses just because the fractions that I can make are relatively inaccurate.

The distance between 2 cities can be represented as d.

Time is d/r if r is rate, so B->NY=d/50

Similarly,NY->B is d/70

Obviously the average speed is 2d/(d/50+d/70), this is just an average time

Now just remove the d and get (d/d)*2/(1/50+1/70)

You can now multiply by the LCM/LCM, which is 350/350.

After calculating you will get 700/12 which is 58.333...(This is how to enter into your RSM browser) Hope this helps. Sorry it is so late.