Question

Lily takes 3 hours to travel from place A to place B at the rate of 60 miles per hour . She takes 2 hours to travel from B to c with50% increased speed .find the average speed from place A to C

Answer 1

The average speed form A to C is 72 miles/hour

Step-by-step explanation:

Average Speed

If an object travels a distance d in a time t regardless of the direction, the average speed is the quotient of the distance over the time:

`\displaystyle \bar v=(d)/(t)`

Lily travels from A to C in two steps:

First, she takes ta=3 hours from A to B at va=60 miles/hour. The distance traveled in that time is:

da=va*ta

da=3*60 = 180

da = 180 miles

Then she takes tb=2 hours to travel from B to C at a speed 50% increased with respect to va, thus:

vb=150*va/100=1.5*60=90

vb=90 miles/hour

She travels a distance:

db=2*90=180 miles

The total distance traveled is

dt=180 + 180 = 360 miles

And the total time taken is

tt= 3 + 2 = 5 hours

Thus, the average speed is:

`\displaystyle \bar v=(dt)/(tt)`

`\displaystyle \bar v=(360)/(5)`

`\displaystyle \bar v=72\ miles/hour`

The average speed form A to C is 72 miles/hour