Question

A train covers a distance of 90 kms at a uniform speed. it would have taken 30 minutes less if the speed had been 15 km/hr more. calculate the original duration of the journey

Answer 1

answer is 5 hour 30 minutes

Answer 2

let speed be x km/h  

increase by 15

=x+15  

original time - time with increased speed = 1/2 hour  

d=90 km  

d/r = t  

90/x-(90/(x+15)=1/2  

multiply the equation by 2x(x+15) to eliminate the denominator

180(x+15)-180x=x(x+15)  

180x+2700-180x=x^2+15x  

 

90x cancels off  

x^2+15x-2700=0  

x^2+60x-45x-2700=0  

x(x+60)-45(x+60)=0  

(x+60)(x-45)=0  

x= 45 km/h