Question 54

A train takes 2 hours less for a journey of 300 km by increasing its speed by 5 km/h. What is its normal speed?

Solution

Time= distance/speed

let unusual speed be x

so (300/x)-(300/x+5)=2

300{(x+5)-x}=2(x+5)x

1500=2x(x+5)

x(x+5)=750

(x^2)+5x-750=0

from this equation, we can find the two zeroes for the equation as -30 and 25

as speed can never be negative,

so x=25 kmph

A is correct choice.

Create a FREE account and get: