Tag Archives: estimation using mass

OS19 Counting Pumpkin Seeds

It’s easy to say the bigger the pumpkin the more seeds inside. But is this really true? And just how many seeds are in a pumpkin, anyway?

One way to find out is to count all of them. As you found out in the last Investigation, there are lots of them. Maybe it’s possible to estimate how many seeds there are.

In this Investigation, you can compare how many seeds are in two different pumpkins, a big one and a small one. You compare two different ways of counting the seeds.

When you are done counting the seeds, you can roast them to eat or save them to grow new pumpkins next year.

 project materials

Question: How many seeds are in a pumpkin?


2 ripe pumpkins (a small one and a big one)


1 Custard cup

3 Medium Empty Bowls

1 Big Empty bowl



Step 1: Open your Science Journal, write Investigation 19 and the date.

mass of cup

It’s important to mass the cup empty before putting the twenty seeds in.

Step 2: Label two bowls 1 and 2. Mass the custard cup and two bowls. Record these in the Table.

mass empty bowl

Be sure to write down the mass of the empty bowl so you can find the mass of the pumpkin seeds later.

Step 3: Cut one pumpkin open.

Step 4: Carefully pull handfuls of the strings and seeds out of the pumpkin dumping them in the unlabeled bowl. [You can use the seeds from Investigation 18.]

pulp and seeds

I like to use a soup spoon to scrape out all the pulp and seeds.

Step 5: Separate the seeds from the strings putting the seeds in Bowl 1. Some of the seeds may be very small and flat. Discard these with the strings.

Step 6: Mass Bowl 1 and the seeds. Record this in the Table.

Step 7: Count out 20 seeds. Put them in the custard cup and mass them. Record this in the Table.

mass of 20 seeds

Does the size of the seeds matter when you get the mass? If you include lots of little flat seeds, how will this change the mass?

Step 8: Count all the seeds moving them from one bowl into the unlabeled bowl. Be sure to add the 20 seeds put in the small bowl after massing them.

Step 9: Repeat with the second pumpkin using Bowl 2.


table 1

How many seeds did you count for each pumpkin?


Pumpkin 1:


Pumpkin 2:

table 2

Counting each pumpkin seed individually takes a long time. Perhaps using seed mass will give an easier way.


Calculate the masses of the seeds [Subtract the mass of the bowl from the mass of the bowl and seeds mass]. Record this in Tables 1 and 2.

Estimate the number of seeds by first dividing the mass of 20 seeds by 20 to get the average mass of a seed. Then divide the mass of all the seeds by the average mass of one seed to get an estimate of how many seeds were in the pumpkin.

Do these two calculations for the second pumpkin.


mass of seeds

Does the pulp or the seeds have more mass?


Compare the total number of seeds from each of the two methods. Are they about the same?

How accurate is using mass to find the number of seeds? Why do you think this?

Which method is easiest to do? Why do you think this?

Do you think different sizes of pumpkins would have different numbers of seeds? Why do you think this?

Do you think different kinds of pumpkins have different numbers of seeds? Why do you think this?

Do you think using more than 20 seeds for a sample would make that method more accurate? Test this and find out.

Can you think of any other ways that might make these methods more accurate? Test these and find out.