Question

Answer this quickly please!
Lisa started to drive from Boston to Washington, DC, which is 440 miles away, at 8:00 AM. For the first four hours of her trip, Lisa was driving at a speed of 50 mph. What was her average speed during the second part of the trip, if she reached Washington at 4:00 PM?

Answer 1

Answer:

$\bar v = 60\,mph$

Step-by-step explanation:

The distance travelled by Lisa in the first four hours of her trip is:

$\Delta s = \left(50\,mph)\cdot (4\,h)$

$\Delta s = 200\,mi$

The distance remaining and her average speed are, respectively:

$\Delta s_{R} = 440\,mi - 200\,mi$

$\Delta s_{R} = 240\,mi$

$\bar v = \frac{240\,mi}{4\,h}$

$\bar v = 60\,mph$