Algodoo

A funny mechanical problem:
There is a drive of two gears of 20 teeth each.
What is the motion of the driven gear if 1 tooth of the driving
gear is broken?
Wrong answer: 1 revolution of the driving gear corresponds
19/20 revolution of the driven gear.
Correct answer:
The driven gear rotates as if the tooth was not broken, because if the driving gear has only
1 tooth, it makes the driven gear move 2 teeth.