Question

An express train takes one hour less than the passenger train to travel 132 km. If the average speed of the express train is 11 km per hr more than the passenger train. What is the average speed of the 2 trains.

Answer 1

Time taken by passenger train $=\frac{132}{x}$ hr

The time taken by the express train $=\{\frac{132}{x}+11\}$hr

Now, according to the question

$\frac{132}{x+11}=\frac{132}{x}+1$

$\frac{132}{x+11}=\frac{132+x}{x}$

$132x=(132+x)(x+11)$

$132x=132x+1452+x^2+11x$

$x^2+11x-1452=0$

$(x+33)(x+44)=0$

$x=-33,-44$

As speed cannot be negative,

Therefore, speed of passanger train $=33km/hr$

and the speed is $33+11=44km/hr$