3030* 100/207.24 is approximately equal to 1500 turns (actually, it is multiplied by 100 here, and the unit is converted into centimeters).
1500*8/ 13 is about 900 revolutions (the number of teeth of the front and rear wheels should be equal, and multiplying by 8 can be regarded as calculating the total number of teeth, and finally dividing by the number of teeth of the front wheel13; Or 1500:x= 13:8, x= 1500*8/ 13) can be calculated in proportion.