Question

The distance between two stations A and B is 160 km. A train covers first 40 km at a speed of 20 km per hour. How fast should the train travel while covering the remaining distance, so that its average speed for the entire journey is 40 km per hour ?

Answer 1

Given that, the distance between two stations i.e. station A and station B is 160 km.

A train covers first 40 km at a speed of 20 km/hr.

{ ∴ d = 40 km and s = 20 km/hr }

We have to find that how fast (means speed) should the train travel while covering the remaining distance, so that its average speed for the entire journey is 40 km/hr.

Here, average speed of the train during whole journey is 40 km/hr. (given)

Now,

Time = Distance/Speed

Time = 160/40

Time = 4 hours

Similarly, time taken by train to cover 40 km at a speed of 20 km/hr.

Time = 40/20

Time = 2 hours

Remaining distance = (160 - 40) km = 120 km

Remaining time = (4 - 2) hours = 2 hours

Therefore,

Remaining Speed = (Remaining distance)/(Remaining time)

∴ Remaining Speed = 120/2 = 60 km/hr.

Answer 2

$\bigstar$ Question :

• The distance between two stations A and B is 160 km. A train covers first 40 km at a speed of 20 km per hour. How fast should the train travel while covering the remaining distance, so that its average speed for the entire journey is 40 km per hour ?

$\bigstar$ Answer :

$\bigstar$ Given :

$\bigstar$ Case - 1 : For 1st 40 km

• Distance between two stations A and B is 160 km.
• A and B is 160 km. A train covers first 40 km at a speed of 20 km per hour.

i.e., d = 40 km , s = 20 km/hr

=> Time = d/s = 40/20 = 2 hr

$\star$ This time is for 1st 40 km.

$\bigstar$ Case - 2 : For total 160 km

$\star$ d = 160 km , s = 40 km/hr

=> t = d/s = 160/40 = 4 hr

$\star$ This time for total distance 160 km.

$\bigstar$ Case - 3 : For remaining and required distance

$\star$ Remaining distance , d = 160 - 40 = 120 km

$\star$ Remaining time , t = 4 - 2 = 2 hr

=> Speed for remaining distance = Remaining distance / Remaining time

=> s = 120/2 = 60 km/hr

                                                                                                     

>>> $\star$ Hope Helps You $\star$ <<<