Question

Places A and B are $100$km apart on a highway. one car starts from A and another from B at the same time. If the car travels in the same direction at different speeds, they meet in $5$hrs. If they travel towards each other they meet in one hr. What is the difference of speeds in Km/hr of the two cars?

Answer 1

Let the speed of car at A be $x$ kmph

and the speed of car at B be $y$ kmph

when the car travel in same direction Relative Speed is $x-y$

$Dist=100km$

$t=5$ hours

$\therefore$ $Dist$ $=S\times T$

$100=(x-y)5$

$x-y=20⟶\left(I\right)$

when car travel in opp direction Relative Speed is $x+y$

$Dist=100$km

$t=1$ hours

$Dist=ST$

$100=(x+y)1$

$x+y=100⟶\left(II\right)$

Solving (I) & (II)

$x-y=20$

$\underset{–}{x+y=100}$

$2x=120$

$x=60$km/h

$y=40$km/h

Speed of the car at $A$ $=60$ km/h

Speed of the car at $B=40$ km/h

The difference of speeds is $60-40=20$