Quote:
Originally Posted by glatt
"The wheels roll without slipping" is impossible. One or the other can roll without slipping, but both can't. Either the blue wheel is in contact with the ground, and the red wheel "slips," or the red wheel is in contact with some sort of raised rail or other surface it can ride on, and the blue wheel "drags."
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I would guess that the "not slipping" is justified in the brain teaser as - the blue wheel doesn't slip relative to the ground, and the red wheel doesn't slip relative to the blue wheel. But the red wheel is being carried forward by the blue wheel.