Find the speed

Question

A car travles 450 mi at a certain speed. If the speed had been 5mph faster, the trip would have been made in 1 hr less time. Find the speed. 

Answer 1

Let x = speed (mi/hr) and let t be # of hrs of travel 450 miles at 'certain speed' x.

 

Distance = speed • time ⇒ 450 = x•t

 

Same distance at rate 5 mi/hr more takes l hour less ⇒ 450 = (x+5)(t-1).

 

Now there are two equations & two unknowns.  Can you solve this system? Hint: t = 450/x; substitute...