Galadriel's Rings

A wizard with a long beard and bright, flaming eyes places a table in front of you. On the table are two circular rings resembling frisbees.

[Two rings of equal size]

The wizard motions to the table. "We call them Galadriel rings after the great elf of Middle Earth, and we use the rings to test humans with whom we come in contact. As you see, one ring is red, the other gold. Both rings are the same size. The red ring is stuck to the table. The gold ring rotates around the red ring, touching it without slipping. When the gold ring has completed a turn around the red one, how many turns has it made around its own axis?"

The wizard offers a reward. "If you answer correctly, we will give you the power of invisibility to use as you like. If you answer incorrectly, we will imprison you in an oubliette."

What is your answer? a) 1 revolution b) 1.5 revolutions, c) 2 revolutions d) 2.5 revolutions e) 3.141... revolutions, f) Not on list.

What do you think is the most common answer given to this problem, and why?

Cliff Pickover