What questions does this picture beg you to ask?
What information do I need to figure out which gear combination would be better to pedal up a steep hill?
What information do I need to gather about my bicycle to figure out the gear sequence I should use from low to high? What do I need to know if I want to know how far I can travel with one pedal if I don’t count coasting?
Gear Inches will tell you the diameter of the wheel that this is equivalent to if you were riding a “high wheeler” or “penny farthing” or just a tricycle. Gear inches times will tell you how many inches the rear wheel will turn with 1 turn of the pedal, without coasting.
How Stuff Works article about how bicycles work: activities/biking/bicycle4.htm activities/biking/bicycle4.htm How Stuff Works article about how gear ratios work: equipment/gear-ratio1.htm equipment/gear-ratio1.htm YouTube video about bicycle gears: