Speed, distance and time relationship:

$\overline{){\mathbf{v}}{\mathbf{=}}\frac{\mathbf{d}}{\mathbf{t}}}$

Average speed:

$\overline{){{\mathbf{v}}}_{\mathbf{a}\mathbf{v}\mathbf{g}}{\mathbf{=}}\frac{{\mathbf{d}}_{\mathbf{total}}}{{\mathbf{t}}_{\mathbf{total}}}}$

We know the total distance but we do not know the total time.

Julie drives 100 mi to Grandmother's house. on the way to grandmothers h's Julie drives half the distance at 40 mph and half the distance at 60 mph. On her return trip, she drives half the time at 40 mph and half the time at 60 mph.

What is her average speed in the return trip?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

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