Distinct points of meeting in a track 
$A$ and $B$ start running simultaneously towards each other from the
two ends of a track $XY$ and the ratio of their speeds is $3$ : $4$.
Every time they meet, they interchange their speeds and also reverse
their directions. At how many distinct points on the track do they
meet each other, if they run continuously between $2$ ends of the
tracks? The length of the track is $100m.$

Now I have understood the problem very well and I tried to solve it as well using general approach  but after few steps I realized that solving it by general common way will be very lengthy and tedious and I was not getting anywhere. 
Then I turned to the solution for this problem and as part of the solution it was given that

It is similar to the case of circular motion where $2$ runners are
running in opposite direction. Hence number of meeting points is $(3 +4)=7$.

Now I am also not able to understand how this case is similar to the $2$ runners running in opposite direction around a circular field. I am aware of this formula to find the number of distinct points for the above case. But I am not able to relate the two cases given as part of the problem.
Please help me with this !!! How can this question be solved in the best way?
Thanks in advance!!!

Let's give each runner a baton, $A$ gets baton $A_1$ and $B$ gets baton $B_1$. Every time the runners meet they exchange the batons. Let's track the movement of the batons. At the beginning, baton $A_1$ moves with the speed $3x$ and baton $B_1$ moves with the speed $4x$. When the runners meet, runner $A$ gets baton $B_1$ and runs in the same direction in which $B_1$ was moving before the meeting and with the same speed $4x$. Similarly, $A_1$ continues to move with the speed $3x$ in the same direction as before. Thus, we can simplify the problem to track two batons that go with the constant speed in the opposite directions. Note that the batons start at the opposite ends of the track $XY$ and move toward each other. When they meet, they cover the length of the track, baton $A_1$ covers $\frac{3}{7}$ and baton $B_1$ covers $\frac{4}{7}$ of the track. Notice that this is equivalent to two batons that move over a circular track of the same length if they start at the same point and move in the opposite directions.
