The speed of the robot on the left is too slow.  The one on the right is ok. It is 24 to 40 or 3 to 5.

The gearing on the left works on the bottom row but the driver gear on the motor meshes with two gears.
The gear train on the right works.  It will be 1 to 5. So it will be 3 times slower than the bot with the motor
with the 24 tooth gear between the 40 tooth gears.