Question

A train covers a distance of 880 km at a constant speed. If its speed would be 15 km / hr more, then it would have taken 6 hours less to cover the same distance. What is the original speed of the train?
1. 40 km / hr
2. 55 km / hr
3. 60 km / hr
4. 50 km / hr

Answer 1

Correct Answer - Option 1 : 40 km / hr

Given:

A train covers total distance = 880km

Formula Used:

Speed = Distance covered/Time taken

Calculation:

Let the speed of the train be x

Time taken by train = 880/x

Now, the increased speed of train be(x + 15)

Now, Time taken by train = 880/(x + 15)

According to the question;

Difference between time taken = 6 hours

⇒ 880/x - 880/(x + 15) = 6

⇒ 1/x - 1/(x + 15) = 6/880

⇒ 15/x2 + 15x = 6/880

⇒ 5/x2 + 15x = 2/880

⇒ 5/x2 + 15x = 1/440

⇒ x2 + 15x - 2200 = 0

⇒ x = - 55, 40

The speed of the train = 40 km/hr