



 
Hi Lanie. Assume that both cars took the same route, so they went the same distance. Remember that velocity (speed) is the distance divided by the time. So we can use algebra to solve this problem.
In particular, let's call the two cars F and S (fast and slow). Then we can double up our equation with subscripts:
If we solve each of these for distance, we have:
But we said that both cars went the same distance, so d_{S} = d_{F} and so
Now look at the times involved. The fast car took 3 hours and the slow car took 3.5 hours, so we can substitute those into the equation:
And since we know the fast car's speed is 10 mph faster than the slow car, we know that v_{F} = v_{S} + 10, so we can substitute v_{S} + 10 in for v_{F}:
Now, you can easily solve for v_{S} and the rest of the questions you are asked. Cheers,  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 