Question

You drive to the store at 20 mph and return by the same route at 30 mph. Discounting the time spent at the store, what was your average speed?

Answer 1

Answer:

Step-by-step explanation:

Average velocity is distance over time.

Let d be the distance to the store.

Therefore the total distance is D= 2d.

Let the time required to go to the store is the time required while going 30 mph plus the time required to go at 20 mph. The equation for time is distance divided by velocity.

Therefore the equation for time is

t = d/20 + d/30 = 3d/60 + 2d/60 = 5d/60 = d/12

The equation for velocity is

V= D/t.

Therefore V= 2d/(d/12)

Using inverse multiplication we get V = 2*d/d * 12

The d’s cancel out so we get V= 24 mph.