The odometer formula for the third grade of primary school: x = X= 1000000*M*N/L m * n/l The odometer consists of a worm wheel and a digital wheel. When the car is running, the transmission shaft drives the first right digital wheel of the odometer through three pairs of worm wheels, so that the number on the first digital wheel is displayed as110km. Starting from the first digital wheel on the left, the transmission ratio of 1: 10 is formed between every two adjacent digital wheels through their internal teeth and the carry digital wheel transmission gear.

When the first digital wheel rotates once, from 9 to 0, the second digital wheel on the left is driven by the internal transmission gear to rotate110 times, increasing1km; When the second digit wheel rotates once, from 9 to 0, the third digit wheel on its left side rotates110, increasing 10km. Other digital wheels are displayed from low position to high position in turn, and the mileage of the car can be displayed by analogy.