Spring is in the air. Honestly, I teach sixth graders. I could tell you exactly when Spring starts without ever stepping one foot outside. Why? Because, like I said, I teach sixth graders. Haha. Anywho…..I live in Oklahoma and if you haven’t heard (with the exception to this last weekends tornadoes) our weather has been absolutely amazing! Perfect temperatures and beautiful sunshine. One whole wall in my classroom is nothing but windows that look out at our school’s courtyard. There are trees, some picnic tables, grass, and some random messes that our science teacher has made. April 22 is also Earth Day, so this would be a super great activity to celebrate.

Our testing is over, so I’ve taught my students all of the skills I am required to teach them this year. This last month is just kind of “play time” for me. This is the time that I can do creative projects, or time consuming lessons that I wouldn’t necessarily have the time to fit into the regular year. While looking out the window, into the courtyard, my brain started churning. I decided I had to come up with some kind of lesson to do outside.

Finally it hit me. We could find the diameter and radius of the trees by measuring its circumference. We have eight trees in our courtyard. This means that with my 25-30 students per class, I could pair them up and there wouldn’t be too much standing around for people to measure trees. I don’t want students standing around waiting, because that’s when you start to have discipline problems.

Here is the activity:

Before the class starts, make signs and attach them to the tree indicating which number tree is which. Numbering the trees will make it easier when comparing the answers the students get. Put the class in groups of two. There are at least two different ways you could have the students measure the circumference of the trees. For one, students could use a long piece of non-stretch twine. Wrap the twine around the base of the tree, and then use a measuring stick to measure the twine. Or you could give each pair a fabric measuring tape (the kind you use for sewing), and wrap it around the tree. Either way will work.

After students finish measuring the circumference of all of the trees, they will then use that measurement to find the diameter and the radius of each of those trees. In order to find the diameter, given the circumference, students must remember the formula for circumference.

C = d * pi (sorry, I don’t know how to find the pi button on wordpress)

If I know what the circumference is, I already know the other pieces to the “puzzle” so it becomes a “solving algebraic equations” problem. For example; if I measure the circumference of the tree and it is 20 inches. I can plug the 20 inches into the formula, I know that pi is 3.14 so I solve for the diameter.

20 = d * 3.14 You would divide both sides by 3.14, and you would get that the diameter is approximately 6.369 inches. Why did I say approximately 6.369? Because 3.14 is an approximation of pi. Pi actually goes on and on forever. Anytime you use 3.14, it will not be an exact answer but an approximation. If you leave the answer in terms of pi, then you have an exact answer. It is also not exact because I rounded the answer.

Once students find the diameter, they simply find the radius by dividing the diameter by two.

Compare the students’ answers once they are finished. You could even graph the different answers they get. You could have them find the mean, median, mode, and range of their different answers. There are a myriad of concepts you could include with this activity.

I have not done this lesson with my classes yet. I plan on doing it tomorrow or Thursday, depending on when they finish the project we have been working on. Below is a copy of the worksheet I will be giving my students to record their answers. I will write a post on the outcome of this activity later, and will include pictures.