Flipping cups

My son has opened a package of cups and distributed them on a table, ready for a party. Some are upright and some are upside down. By flipping two cups at a time, can I get them all upright? (Mason et al, Thinking Mathematically, Addison-Wesley, 1985, p. 170)


Students may ask, "How many cups?" or "How many are upright?"

Does it say? If not, it must be up to you.

Represent with cups or other objects, like coins.

Represent with letters on paper, such as U's and D's.

Work with actual cups or other objects, such as coins.

Your experience

Have you used this problem with a class and seen approaches other than(or more specific than) those mentioned above? Or do you have other comments or criticisms or stories? If so, please tell us!

Last updated 30 November, 2004