Start at 0 on the number line. Flip a penny.

Start at 0 on the number line. Flip a penny. If it is heads, move right a distance of 1 unit. If it is tails, move left a distance of 1 unit. Keep this up. Explore such questions as: What is the probability that you are at a certain position after a certain number of flips? What is the probability that you will ever return to your starting point at 0? This problem treats probability in an elementary way. Students will be able to see how far they can get using elementary counting methods. Many questions can be asked for which elementary counting will not provide complete answers. At the option of the teacher and the class, this problem can incorporate ideas of equally likely outcomes, unequally likely outcomes, and conditional probability. This mathematically rich problem was prepared by the Ohio Resource Center to accompany the Mathematics Program Models for Ohio High Schools developed by the Ohio Department of Education. (author/sw)