Two limos leave South Bend at the same time and travel in opposite directions. One limo averages 65mph and the other limo averages 55mph. After how many hours will the limos be 720 miles apart?

I know how many hours, but how do you define the variables and do it step by step?

Question

Two limos leave South Bend at the same time and travel in opposite directions. One limo averages 65mph and the other limo averages 55mph. After how many hours will the limos be 720 miles apart?

I know how many hours, but how do you define the variables and do it step by step?

anonymous · Answer

since they travel in opposite directions, add their speeds get 120 mph
then 
$$T=\frac{720}{120}=6$$