Question

Margaret drove to a business appointment at 70 mph. Her average speed on the return trip was 60 mph. The return took ⅓ hr longer because of heavy traffic. How far did she travel to the appointment ?

Answer 1

Let d and t be the distance and the time it takes for Margaret to get the place of the appointment.

d is the product of the speed when she was going to the appointment times the time (t):

$d=70t$

d is also the product of the speed when she was going back home times t+1/3:

$d=60(t+\frac{1}{3})$

Make both d equal and find the value of t:

$\begin{gathered} 70t=60(t+\frac{1}{3}) \\ 70t=60t+20 \\ 10t=20 \\ t=\frac{20}{10} \\ t=2 \end{gathered}$

Use this value of t to find d:

$\begin{gathered} d=70(2) \\ d=140 \end{gathered}$

According to this, she traveled 140 miles to the appointment.