Question

A train travels at a certain average speed for a distance of 63 km and then travels a distance of 72 km at an average speed of 6 km/h more than its original speed if it takes 3 km to complete the total journey what is the original average speed

Answer 1

let the original speed of the train be x km/hr

then the increased average speed of train be x+6km/hr

ATQ

=63/x +72/x+6 =3

=63(x+6)+72x/x(x+6) =3

=3x(x+6)=63x+378+72x

=3(x+6)=135x +378

=3x2-117x-378=0

=x2-42x-126(dividing both side by 3)

=x2-42x+3x-126=0

=x(x-42)+3(x-42)

=(x+3)(x+42)

=x=-3 | x=42

so average speed is 42 km/hr.speed can not be negative....

Hope it will help you