Calculating Distance Traveled: Solving for the Unknown in a Multi-Unit Problem

[s9d00ap]

My problem. Amanda took an 8 hour drive. The return trip home took 5 hours and was 21% faster. How many miles did she drive?

 

[topsquark]

There isn't enough information. Is this the whole problem?

Trip out:
[math]D = v_1 t_1 = 8 v_1[/math]

Trip back:
[math]D = v_2 t_2 = v_2 \left [ (1 - .21) t_1 \right ] = 6.32 v_2[/math]

We need some other relationship between [math]v_1[/math] and [math]v_2[/math].

-Dan

 

[castor28]

You can see immediately that something is missing. Imagine you can find a solution $D$ for the distance. How would you known if this represents miles, kilometers, or some other unit ?