Question

Julie drives 100 mi to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at 30.0 mph and half the distance at 70.0 mph . On her return trip, she drives half the time at 30.0 mph and half the time at 70.0 mph . What is Julie's average speed on the way to Grandmother's house?
What is her average speed on the return trip?

Answer 1

Answer:

Explanation:

Given

Distance to grandmother's house=100 mi

it is given that during return trip Julie spend equal time driving with speed 30 mph and 70 mph

Let Julie travel x mi with 30 mph and 100-x with 70 mph

$\frac{x}{30}=\frac{100-x}{70}$

x=30 mi

Therefore

Julie's Average speed on the way to Grandmother's house$=\frac{100}{\frac{50}{30}+\frac{50}{70}}$

=42 mph

On return trip

$=\frac{100}{2\frac{30}{30}}=50 mph$