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10th std · Jul 4, 2009, 08:42 AM

An express train takes 1 hour less than a passenger train to travel 132km between Mysore and Bangalore.If the average speed of the express train is 11km/hr more than that of the passenger train, form the quadratic equation to find the average speed of the two trains.

s_cianci · Jul 4, 2009, 08:50 AM

Let x = the speed of the passenger train. What then, in terms of x, does that make the speed of the express train? Now, time = distance/speed, always. And distance = 132 in both cases here. So, time = 132/speed. And the time for the express train = time for the passenger train - 1. I'll leave it to you to fill in the gaps and solve the resulting equation for x.

Unknown008 · Jul 4, 2009, 08:55 AM

Ok, you need to understand your question. This becomes easy with practice:

Let the average speed of the express train be x km/h.

So, the time taken for the train to travel 132 km is (132/x) h.

The time taken for the passenger train is 1 hour more, so, its time take is [(132/x)+1] h.

Then, the average speed of the express train is 11 km/h more... meaning that x is 11 km/h more than the speed of the passenger train, which is thus (x-11) km/h.

Now, distance = speed x time, and both distances are the same, thus;

$(x)(\frac{132}{x}) = (x-11)(\frac{132}{x}+1)$

Now, expand and simplify to get your quadratic equation. :)