Beacon Lesson Plan Library

Calculating Cats

Sharon Ussery
Hardee County Schools


Come along with the “Calculating Cats” and learn all about calculators and how to add and subtract whole numbers less than 1,000.


The student uses a calculator to explore addition, subtraction, and skip counting.


-Overhead calculator
-Calculator page one per student (see associated file). This file may take a few minutes to download since it contains a graphic.
-Worksheet--one per student (see associated file)


1. Gather enough calculators for each student.
2. Copy calculator sheet and worksheet (one per student) located in the associated file.


Note: This lesson doesn't instruct on using a calculator for skip counting.

1. Use an overhead calculator (can be purchased through any educational math catalog, if you do not have one a picture of a calculator on an overhead projector will do, or see Weblinks for an online calculator to use with a presentation system) to go over the various parts of a calculator. Write the words on the board and make sure all students can read and pronounce them.

2. Show the students how to add and subtract on the calculator. Distribute calculators and allow students to "play" with them for a minute or two. Give students several sample problems, allow them to use the calculators, then ask indiviudals to come to the overhead calculator to demonstrate how they arrived at the answers. Offer feedback and much practice. Circulate as students are the 'teacher' and observe to see if the class members are using the calculators correctly. (Remind them they can 'check' to see if the answer is reasonable: adding two numbers will give a total that is larger than either of the numbers and subtracting two numbers will yield an answer that is less than either of the numbers. The exception is 0.)

3. Distribute the calculator page to each student and have them label each part of the calculator. This can be done in small groups or individual.

4. Review with the students to make sure that they labeled the calculator correctly and understand how to use a calculator.

5. Do a few problems outloud or on the board until the students feel very comfortable using a calculator.

6. Have the students complete the worksheet in the associated file to show an understanding of how a calculator works. Circulate and observe students as they work. Remember, a correct answer is desirable, but correct use of the calculator is the important criteria.


Note: This lesson doesn't assess skip counting.

By using the assessment provided in the associated file, the student demonstrates his/her knowledge of how to use a calculator correctly by adding or subtracting whole numbers from 0 to 1,000. As students work, circulate and observe how they use the calculators to obtain the answers. Correct answers are desired, however, the process of correctly using the calculator is the important criteria.

Web Links

If you do not have an overhead calculator but do have access to a presentation system, this site will allow you to show and manipulate a calculator for students.
Calculators Online

Attached Files

This file contains the calculator to label and worksheet.     File Extension: pdf

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