The ratio between the speeds of two trains is 4 : 5. If the second train runs 800 km in 8 hours

The ratio between the speeds of two trains is 4 : 5. If the second train runs 800 km in 8 hours, then what is the speed of the first train?

A.      80 Km/h

B.      90 km/h

C.      70 km/h

D.      40 km/h

Sol;

Formula Used: 

speed = distance/time

Let the speed of two trains be 4x and 5x respectively 

⇒ Speed of second train = 5x = 800/8 

⇒ 5x =  100 km/hr   

⇒ x = 20 km/hr 

⇒ speed of first train = 4x = 20 × 4 = 80 km/h 

∴ The speed of the first train = 80 km/h