Question

plz solve this problem

Answer 1

speed of train 100 kmph
speed of car 80 kmph

$\frac{400}{st} + \frac{200}{sc} = 390$
ie 800sc + 400st =780sc.st (1)

$\frac{200}{st} + \frac{400}{sc} = 420$
ie 200sc + 400st = 420sc.st (2)

solving 1 &2
600sc = 360sc.st

$st = \frac{600}{6hr} = 100kmph$
sc =80kmph

Answer 2

Given total distance = 600km.

Let the speed of the train = x.

Let the speed of the car = y.

We know that Time = Distance/Speed.

(1)

Given that he covers 400 km by train and the rest by car in 6 hours 30 minutes.

= > (400/x) + (200/y) = 6.5    ------ (1)

(2)

Given that he travels 200 km by train and rest by car,he takes 1/2 hour longer.

= > (200/x) + (400/y) = 7    ------- (2)

----------------------------------------------------------------------------------------------------------------

On solving (1) * 2 & (2), we get

= > (400/x) + (400/y) = 13

= > (200/x) + (400/y) = 7

     ------------------------------------

       600/x = 6

         6x = 600

          x = 100.

Substitute x = 100 in (2), we get

= > (200/x) + (400/y) = 7

= > (200/100) + (400/y) = 7

= > 2 + (400/y)  = 7

= > 2y + 400 = 7y

= > 400 = 5y

= > y = 80.

Therefore, the speed of the train = 100 km/hr and speed of the car = 80 km/hr.

Hope this helps!