Reply To: Lesson 6-1: Question

[Jackilyn Wolford]

<div>I will be using the following problem called Bubble Madness from CPM.</div>

I think this problem will get student’s attention because they get to play with bubbles (that is fun for even 7th graders). Although the problem is laid out in a pretty structured way, I think working with a team, and this hands-on approach to discovering pi, not just being lectured on it, will lead to a memorable lesson.

The idea of the circumference of a circle is similar to the idea of the perimeter for other shapes; it is the distance around the circle. Wrapping a string around a circular object is one way to measure its circumference. In this activity, you will investigate the relationship of the circumference of a circle to its diameter. The diameter is the length from one side of the circle to the other, through its center.

1. Follow the directions below.

   • Obtain a bubble wand, some bubble solution, and construction paper from your teacher.

   • Blow a bubble and allow it to land and pop on your construction paper. You will see a circle on your paper. (If this does not produce a clear circle, try catching the bubble you blow with your bubble wand and then placing it on the construction paper.)

   • Wrap a string carefully around this circle and then stretch it along a meter stick to measure the circumference of the circle. Make your measurement accurate to the nearest tenth of a centimeter.

   • Then use a string and ruler to find the longest measurement across the circle (also accurate to the nearest tenth of a centimeter). This is the diameter.

   Share tasks so that each person has a chance to blow some bubbles and to measure their circumference and diameter. Take data for at least 8 circles of different sizes.

2. Organize your data in a table and then work with your team to decide on an appropriate scale to graph the data carefully on graph paper.

3. Discuss the following questions with your team and be prepared to explain your ideas to the class.

   1. How can you use your graph to show that the circumference and diameter are related proportionally? (Remember that these are measurements and will thus have some degree of error.)

   2. Approximately what is the multiplier between the diameter and the circumference?