This SAT Math question got no correct submissions

[strategy]

http://mindyourdecisions.com/blog/2015/07/05/everyone-got-this-sat-math-question-wrong-can-you-solve-it-sunday-puzzle/#.VZrxi_lVhBc

[Castlereagh]

This is a corollary of the coin paradox: http://mathworld.wolfram.com/CoinParadox.html

[wodenokoto → Castlereagh]

The animation shows 1 revolution for 1 rotation, but the text says its 2.

That is very confusing.

[nitwit005 → wodenokoto]

I was also confused by that until I changed my perspective. Watch the marker inside the circle.

It starts pointing left. Half way around the inner coin it's pointing left again. At the end it's pointing left once more.

That requires two rotations. The curve its graphing confuses things.