Question

Mark leaves the house for school walking at the rate of 4 km. per hour. Two hours later Kris follows Mark at a walking rate of 6 km. per hour. How long will Kris have to walk to overtake Mark?

Answer 1

Their corresponding distances travelled is the same.

let the time taken by Kris be x hours
then time taken by Mark is x+2 hours

6x = 4(x+2)

solve for x

Answer 2

distance = (rate) (time)
Mark rate is 4 kph
Kris rate is 6 kph
Let the time taken by Kris be  x
And Mark be  x + 2
Kris = Mark
(rate) (time) = (rate) (time)
(6) (x) = (4) (x+2)
6x = 4(x+2)
6x = 4x + 8
6x – 4x = 8
2x = 8
x = 4 Kris needs 4 hours