Question

An express train makes a run of 240 km at a certain speed. Another train whose speed is 12 km/hr less takes an hour longer to cover the same distance. Find the speed of the Express train in km/hr

Answer 1

Answer:

116.9 km/hr

Step-by-step explanation:

Let the speed of the express train be s and the time required by that train to cover 240 km be t.

Since distance = rate times time,

rate = distance / time

                                                            240 km

and so, for the express train, rate = ----------------

                                                                   t

To solve this problem, find the rate of the express train first.

                                                                 240 km

For the other train, rate - (12 km/hr) = -----------------

                                                                     t - 1

Substituting (240 km)/1 for rate in the second equation results in:

240 km       12 km         240 km

------------ - ------------- = ------------------

    1 hr            1 hr              t - 1

Simplifying the left side, we get:

 228 km       240 km

--------------- = -------------

     1 hr              t - 1

Note that if we multiply 228 km by 1.053, we get 240 km.

Let's multiply both numerator and denominator of the left side of the above equation by 1.053:

 240 km         240 km

---------------- = --------------

  1.053 hr           t - 1

Then t - 1 = 1.053, and t = 2.053 (hours)

We already know that the speed of the first train is

            240 km

rate = ----------------

                   t

and we now know that t = 2.053 hrs.

Thus, the rate of the express train is

            240 km

rate = ------------------ =  116.9 km/hr

             2.053 hrs                                                       t

Answer 2

Answer:

12.63 km/hr

Step-by-step explanation:

Given the distance=240km

At 12 km/hr it will take =240/12 =20

time for Express train = 20-1=19

speed=240/19=12.63...km/hr