Math Mondays: Finding Pi

Today is Math Monday, and things turned out that we read a math-themed book and then continued with a hands-on activity.

First we read Sir Cumference and the Dragon of Pi. At the beginning of the story, Sir Cumference takes some bad medicine and turns into a dragon. Unfortunately, the people of the castle spot him and are determined to slay him! Sir Cumference's son, Radius, must save his father using a magic potion he grabbed from the castle doctor. But how much does he need? The right dose is the circumference of a circle divided by its diameter...Radius has do some measuring to figure it out! Will he get the right dose?





My kids (PK3 and K) both enjoyed this story. After reading the book, we decided to try to discover the value of pi for ourselves. The kids were enthusiastic and ready to explore!

Supplies:
String
Yardstick, measuring tape, or ruler
Round objects
Notebook
Caculator

I sent the kids to gather some circular objects of differing sizes. Here's what we found:

Then we set to work to measure the perimeter of each circle. Can we use the yard stick to do it? We discussed that we could roll each circle along, but using the string was easier. We quickly discovered that it is very tricky to do this for objects with thin or sloping edges (we ended up skipping the plate). For the others, teamwork helped us get the job done! We laid the string along the yard stick and wrote down the length of the perimeter. We used the yard sticks to measure the diameters of the circles directly. My 5-year-old did a little logging, preferring that I write, but he was all over the calculator. This was our data:

We noticed that we got three different estimates for pi, although they were pretty close together. We took the average of our original three measurements and compared it to the actual value of pi. Not bad! At this point, I had to switch gears to food prep, but the measuring continued.

I love this activity because we didn't need any new supplies, it was simple enough for both kids to get involved, and it touches on a whole bunch of math concepts and skills:

Measuring
Dividing
Calculators
Writing
Decimals
Pi
Accuracy
Averaging