Question

A train travels a distance of 300km constant speed. If the spead of the train is in
creased by 5km/hr the journey would have taken 2 hours less. find the original spead
of the train.

Answer 1

☞Question.

A train travels a distance of 300km constant speed. If the spead of the train is in

creased by 5km/hr the journey would have taken 2 hours less. find the original spead

of the train?

☞Solution.

→Distance to be covered = $\sf\green{300km}$

→Let normal speed of the train = $\sf\green{xkm/h}$

→ Normal duration of the journey, Time = $\sf\green{ 300/x}$ hours.

→With increased speed of $\sf\yellow{5}$kmhr journey time = $\sf\green{300/(X+5)}$= Time - .$\sf\green{2}$

→Time = $\sf\green{300/n}$___( i )

→Time -2 = $\sf\green{300/(n+5)}$___( ii )

☞Subtract ( ii ) from ( i )to get

➝$\sf\green{2 = 300/n -300/(n+5)}$

➝ $\sf\green{2n(n+5) = 300(n+5) - 300n= 1500}$

➝ $\sf\green{n(n+5) = 750}$

➝$\sf\green{n^2+5n-750 = 0}$

➝$\sf\green{(n+30)(n-25) = 0}$

➝$\sf\red{n = 25 km/h}$

☞The normal speed of the train is $\sf\red{ 25 km/h}$ kmph. Answer [The negative value of$\sf\red{n = \: 30}$ is unacceptable, here.