Conclusion: The number of teeth of a gear is inversely proportional to the number of turns it makes. Solve with the knowledge of inverse proportion in mathematics!
A turns four times and B turns three times. Their tooth ratio is:
Number of teeth of gear A: Number of teeth of gear B = 3: 4 = 15: 20.
B turns four times and C turns five times. Their tooth ratio is:
Number of teeth in the second round: Number of teeth in the third round = 5: 4 = 20: 16.
Number of teeth in gear A: number of teeth in gear B: number of teeth in gear C = 15: 20: 16.