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MathNet 1995 — Part 01 Question 13

Math Olympiad Vault · MathNet 1995 — Part 01

Question 13

The following construction is used for training astronauts: A circle $C_{2}$ of radius $2R$ rolls along the inside of another, fixed circle $C_{1}$ of radius $nR$, where $n$ is an integer greater than $2$. The astronaut is fastened to a third circle $C_{3}$ of radius $R$ which rolls along the inside of circle $C_{2}$ in such a way that the touching point of the circles $C_{2}$ and $C_{3}$ remains at maximum distance from the touching point of the circles $C_{1}$ and $C_{2}$ at all times (see Figure 3).

How many revolutions (relative to the ground) does the astronaut perform together with the circle $C_{3}$ while the circle $C_{2}$ completes one full lap around the inside of circle $C_{1}$?

Question illustration
Figure 3