When a pair of gears are engaged, a wheel rotates a tooth, and b wheel also rotates a tooth; So: number of teeth of wheel A x number of turns of wheel A = number of teeth of wheel B x number of turns of wheel B = constant.

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.