Two trains, each with 20 identical cars, were moving towards each other on parallel tracks at constant speeds. Exactly 36 seconds after the first cars of the trains met, passenger Vova, sitting in the fourth car, passed passenger Oleg from the oncoming train, and another 44 seconds later, the last cars of the trains had completely passed each other. In which car, by count, was Oleg traveling?
Let's assume that the first train (in which Vova was traveling) is stationary. Then the other train was moving relative to the first, covering a distance equal to $20+20=40$ carriages in $36+44=80$ seconds, which means it was traveling at a speed of 0.5 carriages per second.

From the moment the first carriages of the trains met until Oleg caught up with Vova, 36 seconds passed. This means Oleg traveled a distance equal to 18 carriages in that time. Therefore, at the moment the first carriages met, the distance between Vova and Oleg was 18 carriages. Thus, if we do not count the carriages in which they were traveling, there were 17 carriages between them. Vova was traveling in the fourth carriage, so there were 3 carriages of the first train and 14 carriages of the second train between them. Therefore, Oleg was traveling in the fifteenth carriage of the second train (see the figure).

![](https://cdn.mathpix.com/cropped/2024_05_06_c9b930b00ea53112180dg-12.jpg?height=146&width=866&top_left_y=1636&top_left_x=596)

## Answer

In the $15-$th carriage.