Beacon Lesson Plan Library

Estimation in a Jar

Amanda Ellis


Fill a jar with goodies and guess what happens! Use some of your favorite teacher “stuff” for students to use to estimate, group, count, and journal.


The student counts orally to 100 or more by 2s, 5s, and 10s with or without a hundred chart.

The student uses concrete materials, pictures, and symbols to show the grouping and place value of numbers to 100 or more.

The student counts and groups 11 or more objects into tens and ones (for example, 3 groups of ten and 4 more is 34 or 30+4).

The student describes thinking when solving number problems.

The student estimates the number of objects, explains the reasoning for the estimate, and checks the reasonableness of the estimate by counting.


-Clear jar- approximately ˝ gallon size
-Approximately 100 or less items (all the same) to fill the jar
-Journal page
-Rubric (see attached file)


1. Fill a jar (approx ˝ gallon size) with 30-100 items. Items should be the same.
2. Count the number of items in the jar to insure it is in this range.
3. Write sentence frames on the board (“I think there are ____ (number) _____(items) in the jar because . . .” And “There were actually _____ (number) _____(items) in the jar. My estimate was too high/too low.”
4. Reproduce chart on the board (see Procedures #8).
5. Download associated file “Rubric for Estimation in a Jar”. Have a copy for each student.
6. Arrange students into groups of 2-4.


1. Locate a clear glass or plastic jar (about ˝ gallon). Fill it completely with an item that will require less than 100 but more than 30 to fill (boxes of raisins, plastic cars, etc.). Use your imagination and connect it to an existing theme (candy corn in the fall, plastic fish for an ocean unit, etc.).

2. Put the jar on display in the classroom. Tell students that they will be estimating how many are in the jar and provide them an opportunity for investigation prior to the lesson.

3. To begin the lesson, discuss possible strategies for estimating the amount of items in the jar without opening it and counting. Include affirmative and corrective feedback.

4. List key words that were included in the discussion on the board (including: about, big, small, near, closer to, between).

5. Ask students to complete the following sentence frame in their journals, “I think there are _____(number) _____(item) in the jar because________________________________________. Rehearse sentences before students begin to write.

6. After students record estimates, dump some of the contents of the jar in the middle of each table of no more than 4 students until the jar is empty.

7. Review counting by 10’s to 100. Write them on the board. Ask each table to make groups of 10 from their items. The extras that could not make 10 should be separated from the groups of 10.

8. When all the tables have finished making their groups of 10, each table reports to the class the groups of 10 and ones at their table and it is recorded on the board. This is done as a whole group activity with guidance and support. Example: “John and Sara’s table had 2 groups of 10 and 3 ones. How many groups of 10 are there? How do we write 2 groups of 10? How many ones were left over that could not make a 10? How do we write that? If we put the tens and ones together, what number do we have? Ten, twenty, twenty-one, twenty-two, twenty three.”

9. After recording all groups and keeping items separate in the student groups, count together each table’s groups of 10 for a total of tens.

10. Record the total ten and then count on together the ones from each table. Write the total on the board.

11. Allow students time to record the total amount on the journal page by drawing groups of tens and ones that represent the class total.

12. On the same journal page, students will complete the sentence frame, “There were actually _____ (number) _____(items) in the jar. My estimate was (too high/too low).”


Note: This assessment only addresses counting by 10's.
Students will complete a journal page that includes a description of their thinking when solving an estimation problem as a formative assessment for this lesson. An “Estimation in a Jar” rubric is included to assess the lesson. (See attached file)

This journal entry will include an estimation of the number of objects, reasoning for the estimate, and a picture showing how they checked the estimate by counting.

Also included in the rubric assessment are performance tasks. These tasks include counting orally to 100 by 10’s without a hundred chart (partial coverage), using concrete materials, pictures and symbols to show the grouping and place value of numbers to 100 and counting and grouping 11 or more objects into tens and ones.


Filling the jar weekly/periodically with various items and using past items as references could extend this lesson. The results could then be graphed each period for comparison.
Additionally, estimation could be expanded to include larger numbers more than 100.
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