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MathNet 2025-part-02 — 186 problems (EN–VI) Question 166

Math Olympiad Vault · MathNet 2025-part-02 — 186 problems (EN–VI)

Question 166

A pond has $2025$ lily pads arranged in a circle. Two frogs, Alice and Bob, begin on different lily pads. A frog jump is a jump which travels $2$, $3$, or $5$ positions clockwise. Alice and Bob each make a series of frog jumps, and each frog ends on the same lily pad that it started from. Given that each lily pad is the destination of exactly one jump, prove that each frog completes exactly two laps around the pond (i.e. travels $4050$ positions in total).