Eight hours for a 600 km journey, when 120 km is done by train and 480 km by car.
It takes 20 minutes more if 200 km is done by train and 400 km by car.
Formula used:
Speed = Distance/Time
Calculation:
Let the speed of the train be x km/h
And the speed of the car be y km/h
⇒ 120/x + 480/y = 8
⇒ 120(1/x + 4/y) = 8
⇒ 1/x + 4/y = 1/15 ...i)
In the second condition
⇒ Total time = 8 + 20/60 = 25/3 hr
∴ 200/x + 400/y = 25/3
⇒ 200(1/x + 2/y) = 25/3
⇒ 1/x + 2/y = 1/24 ...ii)
After solving equation (i) and (ii)
(By substracting equation 2 from equation 1)
⇒ x = 60 km/h
⇒ y = 80 km/h
Ratio of the speed of train and car is
⇒ 60 : 80
⇒ 3 : 4
∴ The ratio of the speed of train and car is 3 : 4.