I’ve been busy this past week working on “Pumpkin math” with my grade 5 and 6 students.
Every Halloween our four classes of junior students look forward to working together in groups of four to carve their jack-o-lanterns. My students worked to estimate and then calculate the total number of pumpkins our staff would need to purchase. They figured out the number pumpkins each staff member would be responsible for purchasing. They also calculated the total cost of the pumpkins and the amount of money each teacher would spend purchasing their share of the pumpkins. The kids worked enthusiastically and collaboratively to solve their questions and their were many EUREKA moments!
Tomorrow, before carving our pumpkins, I will challenge my students to reasonably estimate the number of seeds in each pumpkin and the total number of seeds all the pumpkins will produce.
On Friday evening while carving our pumpkin with my 7 year old I wondered aloud how many seeds would be in our pumpkin. Kai thought for a second and said “500” and so my “teachable math moment” was born. I told Kai that I knew, on average, that each “section” of pumpkin contained approximately 16 seeds. Kai thought we should count the sections. After counting and double checked we confirmed that there were 22 sections.
I discussed with him if he thought that his estimate was “reasonable”. He said, “Well it’s big pumpkin with a lot of sections, so ya 500 sounds about right.” I pushed a bit and shared aloud my calculations using our known information (# of sections and average # of seeds per section) to come up with my “calculated” estimate.
“So”, he said, “I think there’s about 100 more seeds in the pumpkin than you”. We were both eager to dig into our pumpkin.
After collecting all the seeds Kai needed to devise a plan for counting and calculating them.
At first, he simply started to count them, however, he found himself losing track.
Then he devised this plan:
By grouping in tens, he was able to count and recount more efficiently. He counted by tens and I took the opportunity to show his how 16×10=160.
He encountered another problem; he was running out of room. He counted out 20 piles and decided to make a group of 2oo.
We were getting there! Kai persisted to count out more groups of 10 and when he had 10 more groups, decided to make a group of 100.
With a group of 200 and a group of 100, there weren’t many seeds left to count. Kai went back to his original strategy of counting out groups of 10. He made 8 more and had 5 left over. Mom got involved for the final count (after we did all the hard work!).
We confirmed there was a total of 385 seeds in our jack-o-lantern which was pretty close to my calculated estimate of 352 and Kai’s estimate of 500.
After a lot of thinking we were hungry! Those pumpkin seeds sure tasted great! HAPPY HALLOWEEN!
If you haven’t yet carved your pumpkin and are up to a little “pumpkin math”, our math question is below.
Update: Mrs. MacLean’s Grade 3/4 Class from Ottawa did a little pumpkin seed math of their own!
Did the “rule” of 16 seeds per section apply?