Gear ratio
The gear train above shows three intermeshing spur gears. The gear ratio of this gear train is 18:18 or 1:1.Since the driver and the follower are the only two gears involved in calculating the gear ratio the intermeshing gears in between are insignificant to the ratio.
The gear ratio of the gear train above is 8/18.or 4/9. Notice the direction of the follower in each gear train.