Pumpkin Math Part 2

Junior (Age 9 – 12)

Curriculum Goal

Junior: Geometry and Spatial Sense/Measurement

  • Use appropriate metric units to estimate and measure length and mass.
  • Solve problems that involve converting larger metric units into smaller ones, and describe the base ten relationships among metric units.


  • This lesson is Part 2 of 2 of Pumpkin Math. Part 1 explored circumference and height using non-standard measurements. In Part 2, students build on their knowledge by taking measurements using standard units and converting between different units of measure.
  • Students face the educator in a circle with the pumpkins in the center.
  • For the measuring activity, students work in small groups of four to five at their workstations.


In-person version

  • The same 3-6 pumpkins of varying sizes from Part 1 of this lesson
  • Weighing scale (in pounds and kilograms)
  • Whiteboard and erasable markers
  • Ribbons (plastic or fabric)
  • Scissors
  • Rulers
  • Measuring tape
  • Cube blocks
  • Pumpkin measurement handout – one per child (Appendix B)

Online version

  • Video conference capabilities



·      Review what was learned in Pumpkin Math Part 1 with students and introduce new knowledge:

o   Yesterday, we came up with ways we could measure these pumpkins. We learned that the circumference is measured at the widest part of the pumpkin. We also looked at how to accurately measure the height of the pumpkins using a ruler.

o   Today, we are going to build on this knowledge by measuring and recording the circumference and height of the pumpkins using standard measurement units. We are also going to determine the pumpkins’ weight in metric and imperial units.  

Measuring the Circumference, Height and Weight of Pumpkins

  • If needed, briefly model for students how they can use a weighing scale to measure the weight of the pumpkins. Give them some advice, such as ensuring the pumpkin rests in the middle of the scale and not on the edge in order to get the most accurate measurement, and ensuring they aren’t holding the pumpkin while it’s on the scale so that the scale only measures the pumpkin’s weight, etc.
  • In small groups, have each student measure the circumference, height and weight of a pumpkin. They should record their findings on their Pumpkin Measurement handout (Appendix B).
    • Have rulers, measuring tape and cube blocks available for students at their tables/workstations.
  • Each group can start with one pumpkin and rotate with other groups after they have had the chance to record the measurements for their pumpkin.
  • If there are not enough scales for each group to have one, have one group start with the scale to measure and record their pumpkin’s weight. Circulate the scale so that each group has the opportunity to measure the weight of as many pumpkins as possible.


  • After each group has completed their measurements, bring the class back together as a whole group.
  • Take up the weight, height and circumference measurements:
    • To start, ask someone from each of the groups to share the weight of Pumpkin A. Determine whether there is consensus among the groups.
      • Account for measurement error, acknowledging that the numbers may not be exactly the same, but should be relatively close in range.
    • After hearing from each group, share the weight you determined for Pumpkin A and add it into the table (Appendix B). When I weighed Pumpkin A, it was ___ pounds. How can we express its weight in grams?
    • Model the conversion between grams, kilograms and pounds, bringing attention to the connections between the place value of the numbers and how that gets reflected in the conversions.
      • Depending on the capabilities of your students, you may choose to omit the weight in pounds. It is included here because weight is often measured in pounds. Students may wish to convert the weight from metric to imperial.
    • Work through as many conversions with the students as needed.
  • Take up the heights of each of the pumpkins, first asking the students to share their findings, and then sharing your measurement and writing it into the table (Appendix B). For one or two of the examples, model the conversions between millimeters, centimeters and meters.
  • Take up the circumferences of each of the pumpkins. For one of two of the examples, model the conversions between the millimeters, centimeters and meters.

Look Fors

  • Are students able to accurately measure the height, weight and circumference of the pumpkins using standard and non-standard units of measurement?
  • Can students recognize the relationships between units of measure and be able to convert between them?
  • Can students describe the base ten relationships among the metric units?


  • Encourage students to determine the capacity (volume) for each of the pumpkins using the height measurement and the volume formula for a sphere.


We thank educator Zoe Donoahue for inspiring us with this lesson. This lesson is an adaptation of an activity Zoe conducts with her Grade 5 students at The Dr. Eric Jackman Institute of Child Study Lab School at the Ontario Institute for Studies in EducationUniversity of Toronto.

Share this lesson

Share on facebook
Share on twitter
Share on email