Problem Solving

Question

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

Answer 1

let v be current speed, and t be the time for speed v+5

(v+5)*t = 450  => vt + 5t = 450

v*(t+1)=450   => vt + v =450

 

so vt + 5t = vt + v   => v=5t

so 5t*(t+1)=450  => t*(t+1)=90

t and t+1 are consecutive number, so t = 9

so v=5t = 5*9 = 45