The ratio between the speeds of two trains is 5 ∶ 7. If the first train covers 300 km in 3 hours, then the speed (in km/h) of the second train is
A. 100
B. 300
C. 140
D. 200
Sol:
Let the speed of the first train be 5x and the speed of the second train be 7x.
Speed of the first train = Distance / Time = 300/3 = 100 km/hr
According to the question: 5x = 100 ⇒ x = 20
∴ The speed of the second train = 7x = 7 × 20 = 140 km/hr.
