Chapter 4.8, Problem 18P

To determine

To Find: when will B overtake A for the given condition.

Answer to Problem 18P

  $\frac{s-r}{sq}$

Explanation of Solution

Given:

Car A and B travel on the same road their speeds are $r\&s\text{km/h}$ .

  $t$ is the A’s time of start and A starts q hours before B.

Calculation:

Since, A starts q hours before B therefore B’s time will be $t-q$ .

To overtake distance covered by both have to be equal therefore.

  $\begin{array}{l}rt=\left(t-q\right)s\\ rt=st-qs\\ qs=st-rt\\ qs=\left(s-r\right)t\\ t=\frac{s-r}{sq}\end{array}$

Therefore, the answer $\frac{s-r}{sq}$ .