Question

Two persons goes in the same direction from the same place by car then the distance between them in $4$ hours is $9km$. When he goes in the opposite direction then the distance between them is $350km$. Find the speed of their cars.

Answer 1

Let $s_1$ and $s_2$ be the speed of two cars.

When the cars are moving in the same direction-

If the two objects move in the same direction with speeds u and v,

then Relative speed = difference between their speeds = u-v.

$s_1-s_2=\frac{9}{4}.....\left(1\right)$

When the cars are moving in the opposite direction-

If two objects are moving in opposite directions towards each other at speeds u and v,

Then Relative speed = Speed of first object + Speed of second object = u+v.

$s_1+s_2=\frac{350}{4}.....\left(2\right)$

Adding equation $\left(1\right)\&\left(2\right)$, we have

$2s_1=\frac{350+9}{4}$

$s_1=\frac{89.75}{2}=44.875km/h$

Substituting the value of $s_1$ in equation $\left(1\right)$, we have

$s_2=44.875-2.25=42.625km/h$