Question

A train takes 2 hours less for a journey of 300km. If

the speed is increased by 5km/hr from its usual

speed, find the usual speed of the train.​

Answer 1

Answer:

Let the usual speed of the train is x km/h.

D=300 km (Given)

Speed= time/distance

Time= 300/x

After increasing the speed of the train ;

New speed is (x+5) km/h

Time= 300/x+5

Now, difference between the time taken by usual speed and after increasing speed of the train is two hours. Therefore,

300/x-300/x+5=2

⇒300( 1/x-1/x+5) =2

x+5-x/x square+5x=2/300

5/x square +5x =1/150

⇒x square +5x−750=0

⇒x square +30x−25x−750=0

⇒x(x+30)−25(x+30)=0

⇒(x+30)(x−25)=0

⇒x=25,−30

Ignore the negative value of the speed.

Hence, the usual speed of the train is 25 km/hr.