Before they even poured their cereal yesterday, my kids were already bickering about the pumpkins they had picked at the pumpkin patch last week.
“My pumpkin is bigger than yours!”
“No, MINE is bigger!”
“Mine is taller!”
“But mine is bigger around!”
I was tempted to throw both pumpkins in the trash and move on to spelling. But then I realized that this argument actually had an important mathematical question at its core: What does it actually mean when we say that something is “bigger”?
What Does It Mean to Measure Something?
Most objects can be measured in many different ways.
For example, take a plain old cardboard box.
If you want to check whether a certain lamp will fit in it, you would measure its length, height, and width.
But if you want to check your shipping costs, you would weigh the packed box.
And if you want to know how big a bag of packing peanuts to buy, you’ll need to estimate its volume.
To adults, it’s obvious that before you can measure something, you have to decide what attribute of the object you’re going to measure. But for kids to learn this, they need a lot of hands-on, real-life measurement practice.
So, before we got out the rulers, I had my kids take a look at the pumpkins and decide what attributes of the pumpkins they were going to measure. They chose:
- Distance around
- Height of the stem
And so, the Great Pumpkin Competition began!
What You’ll Need for Measuring Your Pumpkins
To do this activity at home, you’ll need:
- 2 similar-sized pumpkins
- Ruler or yardstick
- Cloth tape measure
- Kitchen scale
- A container big enough to hold each pumpkin (a big soup pot worked well for me)
- A dishpan or storage tub or other container big enough to hold the container that holds the pumpkin
- Large measuring cup
- Paper and pencil for recording measurements
(If you don’t have one of the tools, it’s fine to just skip that measurement.)
Before You Begin
Before you begin, take a few moments to talk about the different measurement tools with your kids and make sure they’re familiar with all of them. Point out the inches and centimeter sides of the rulers and decide which measurement system you’re going to use.
Start a simple chart for recording your measurements. You can see how my son decided to record the measurements below. Have your children add each measurement to the chart as you go.
Measure the Pumpkins’ Heights
Let’s get measuring! Start with a concept your kids are already very familiar with: height.
Show your kids how to place the zero mark on the ruler at the bottom of the pumpkin and measure its height. (Let your kids vote on whether or not to include the stem. Either way is fine–what’s important is that they think about how the stem adds to the height of the pumpkin. My kids wanted to measure the stem separately.)
Have your children record the heights on their papers.
Measure the Pumpkins’ Circumferences
Use the cloth tape measure to measure around the fattest part of each pumpkin. This measurement is often longer than kids expect!
Weigh the Pumpkins
First, have your children hold a pumpkin in each hand and guesstimate which is heavier. This helps kids connect the number on the scale to their everyday experience.
Then, weigh the pumpkin using the kitchen scale.
Measure the Pumpkins’ Volume
Now comes the really fun part: measuring the volume of each pumpkin. You’ll want to move to the kitchen for this!
Find a container big enough to hold the pumpkin. Fill it to the brim with water and put it inside a larger container. Then, push the pumpkin into the water until it is just submerged.
Lots of water will slosh over the sides—this is my kids’ favorite part!
Remove the smaller pot holding the pumpkin.
The water left in the big container is the amount of water that the pumpkin displaced.
So, this amount of water equals the volume of the pumpkin. Measure the water with a large measuring cup to find the volume of the pumpkin.
Compare the measurements for each pumpkin. Discuss with your children whether their was a clear winner. Can you say for sure that one pumpkin is “bigger”?
Part of the beauty of real-life measurement activities is that they’re not cut-and-dried. Kids have to use reasoning and common sense to figure out how to take the measurements accurately.
Here are just a few of the questions my son and daughter puzzled over in this activity:
- How do you use a tape measure? What’s the difference between a tape measure and a ruler?
- How do you measure the height of a pumpkin when the top is uneven?
- What unit should we use on the kitchen scale? Pounds? Ounces? Grams?
- Is it fair to measure the stems when one of them is broken?
- How accurate do the measurements need to be?
- One pumpkin is 7 and 1/4 inches tall, and the other pumpkin is 7 and 1/8 inches tall. How accurate are our measurements? Have we measured accurately enough to declare a winner for height?
Here were my family’s results, as recorded by my eight-year-old:
My five-year-0ld was very disappointed to find that her pumpkin was smaller than her big brother’s in every attribute but height. Thankfully (both for her and for my sanity), her big brother didn’t rub it in too much.
Sibling bickering doesn’t always end so happily (and mathematically) at my house, but this silly argument was a great inspiration for a hands-on pumpkin measurement activity. Give it a try with your own kids for some fun measurement practice!