Question

4. A train covers a distance of 90 km at a uniform
speed. Had the speed been 15 km/hr more, it would
have taken 30 minutes less for the journey. Find the
original speed of the train.
(ICSE)​

Answer 1

Step-by-step explanation:

let the original speed of train be x km /hr

then increase speed = x+15 km/hr

usual time =90/x hr.

new time =90/x+15 hr.

according to the question

90/x -90/x+15 =1/2

90 ( x+15-x /x (x+15)) =2700

x2+15x-2700=0

x2+60x-45x -2700=0

x (x+60)-45 (x+60)=0

(x+60)(x-45)=0

x= -60 or 45 ans.

hope it will help u!!!