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srinivashd · Mar 3, 2011, 05:31 AM

An epress train takes 1 hour less than a passenger train to travel 152 kms between mysore and banglore.if the average speed of the express train is 11 km/hr more than that of the passenger train,find the average speed of the two trains.

galactus · Mar 3, 2011, 05:52 AM

The passenger train travels:

rt=152

The express travels:

(r+11)(t-1)=152

Two equations with two unknowns.

Solve for r. Now, you have the rate of each train.

To find their average, do not fall into the trap of:

$\frac{r_{1}+r_{2}}{2}$

After you have the two rates, use:

$r_{ave}=\frac{2r_{1}r_{2}}{r_{1}+r_{2}}$

Just let the rate of the passenger train be $r_{1}$ and the rate of the express, which is 11 more, be $r_{2}$