Let t = travel time of the cyclist
then ,
(t+1) = travel time of the runner (he start 1 hr before the cyclist)
When the cyclist overtakes the runner, they will have traveled the same distance
Write a distance equation: dist = speed * time
Cyclist dist = runner's dist
20t =4*(t+1)
20t =4t+4
20t-4t = 4
16t = 4
t = 4/16 = 1/4
t = 1/4 hr for the cyclist to catch the runner
The amount of time that the cyclist travels before overtaking the runner = 1/4 hr or 15 minutes