In a game of 12 players that lasts for exactly 75 minutes there are 6 reserves who alternate equally with starting players. It means that all players, including reserves, are in the game for exactly the same amount of time. How long is this?
5 people entered a train carriage with only 2 seats not occupied. The 5 people took in turn so each person had equal time to sit. if the total journey took 1 hour 10 minutes, how long did each person have the seat for?
These questions are very similar have similar working techniques. I would like to know what you call these types of question and how you work it out?
I think in puzzle category. You can solve these questions by an equation $$\frac{x}{y}\cdot z,$$ where $z$ is your time, $x$ is number of "places" and $y$ is the number of pepole.
For example, in your first question, $$x=12,\quad y=18,\quad z=75.$$