a. Put a stick or pencil through the center of each gear. Try putting them together, two at a time, by fitting the notches of one into the notches of the other. Use the small one to turn the big one. Use the big one to turn the medium one. Use the medium one to turn the big one and then the small one.

b. Download and print the chart below, fill it by using your gears. Make a red mark on the rim of each of your gears. Fit Gear A into Gear B at the point at which the two red marks touch. Turn Gear A one full turn; how many turns does Gear B make? Is it fewer than Gear A or is it more than Gear A? Fill in the chart accordingly. For example, if for every turn that Gear A makes, Gear B turns 3 times, write “3” on the chart and fill in the ratio as 1:3. (The ratio is however many times the second gear turns in respect to one turn of the first gear.)

Click on the Activity button and complete all the gear combinations on the chart below.