4th Grade Geometry - Pi and the Geometry of Circles

Last week in Geometry the students did a hands-on activity where they measured the circumference and diameter of a variety of circular shaped objects.  The students worked at measuring old coffee cans, rolls of masking and duct tape, Frisbees, and hula hoops.  They then divided the circumference by the diameter and came very close to calculating Pi!

This week students used their new found knowledge of Pi to calculate the circumference and diameter of other circles.  This presented new challenges as they began using calculators to figure multiplication and division using Pi or 3.14.  Working with decimals and calculators like this can lead to issues of lack of or over confidence.  Many of the students are apt to take whatever answer comes from the calculator as correct no matter how outrageous.  We are working on estimating the answer to the problem in an effort to check the answer from the calculator.  Often students have hit the wrong keys on the calculator and by estimating they hopefully will see that some answers don't make logical sense.

After 3 or 4 successful calculations the students find this to be just as routine as all of the other work we have done.  With hard work and a cycle of success, the students are ready for increasingly difficult challenges.

Some students have asked for a challenge problem to work on at home.  Below you'll find an archery target.  Calculate the circumference of each zone of the target including the yellow or gold center.

Remember that the formula is:

C = d X Pi       and        Pi = 3.14