Question

Denise has 2 hours to spend training for an upcoming race. she completes her training by running full speed the distance of the race and walking back the same distance to cool down. if she runs at a speed of 7 mph and walks back at a speed of 3 mph, how long should she plan to spend walking back?

Answer 1

Let the distance of the race be d miles. We can now write the equation:
$\frac{d}{7}+\frac{d}{3}=2$
which when solved, gives the value of as 4.2 miles.
The time to walk 4.2 miles at 3 mph is 4.2/3 = 1.4 hours.

The answer is 1.4 hours or 1 hour 24 minutes.