Number 23. The picture shows three gears with a black gear tooth on each. So we have a black tooth here, here, and here. Which picture shows the correct position of the black teeth after the small gears? This one has turned a full turn clockwise. Okay, so the first thing we can do is we can count how many teeth each gear has. So this small gear has 10 teeth, the dark blue gear has 13 teeth, and this lighter blue has 13 teeth as well. So these two are big, this one is the small one, clearly. So what happens when this small one turns? Well, when the small one turns clockwise, this dark blue gear turns counterclockwise. Because it just pushes it this way, and that direction is counterclockwise. Well, the dark blue green is now attached to this light blue green. The light blue green is only turned by this dark blue green, which is going counterclockwise. So the light blue gear goes clockwise. Now, what we can do is we look at how big this is. So if this moves one space, then this is also going to move one space. So extrapolating out, if this small gear moves 10 teeth down, this big gear will also move 10 teeth down. And then this one will also move 10 teeth. Just remember that for this dark blue, we would move 10 teeth counterclockwise. For this light blue, we would move 10 teeth clockwise. Counting out our positions, we would get something that looks like answer A. Just real quick, once this small gear is on a full rotation, this should be in the exact same place as it is right now because it's a full rotation. When it's done that, this dark blue will be going counterclockwise. So we count out 10 positions. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. And then we do the same thing with this light blue, except now we go clockwise. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. That pretty much maxes it up exactly with A. That is our answer.

gear rotation

clockwise rotation

tooth alignment

gear teeth

mechanical analysis