Addition and Subtraction Strip Board

Start by watching this sample lesson from our Guidepost Homeschool platform that will familiarize you to the Addition and Subtraction Strip Board in use.

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Setup - Carefully remove all packaging material. Note that some Montessori parts are very small – be mindful not to inadvertently discard anything.

When not in use, store this material with the control charts on the strip board, and the wooden strips in their boxes on top of that. Alternatively, control charts can be stored separately from the rest of the material (e.g.displayed on a stand, letter sorter, or in a napkin holder) if it is too tempting to peek at them while doing the work itself.

Using for addition: When ready to do addition with the strip board, bring all items to a child-height table. Make sure you have the addition side facing up (has a red vertical line after 10), then set the strip board at the front of the workspace. Arrange the blue strips from 1 at the bottom and 9 at the top in the top left area above the board. Align all strips in a straight line at the left side. Next, arrange the red strips with 1 at the bottom and 9 at the top in the top right area above the board, again aligning all strips in a straight line at the left side.

A blue strip is used for the first addend, and a red strip for the second addend in an addition problem. The sum is the number directly above the end of the red strip. This picture shows the setup as well as how to place the strips for the addition problem of 5 + 7 = 12.

Using for subtraction: When ready to do subtraction with the strip board, make sure you have the subtraction side of the board facing up (has a blue vertical line after 9), and arrange the blue strips at the top left of the board (no need for red strips). To the left of the board and blue strips, arrange the natural wooden strips from longest to shortest and align them at the right edge.

A wooden strip is used in subtraction to isolate the minuend (the beginning, larger quantity). A blue strip is used in subtraction to represent the subtrahend (the quantity being ‘taken away’). The number that’s visible to the left of the blue strip is the difference between the two. This picture shows the setup for subtraction as well as how to place the strips for the problem of 15 – 8 = 7.

Using for exploring quantities:When ready to use the strip board for exploring quantities: Set up all three kinds of strips as previously described. Use a wooden strip to block off numerals at the top of the board that are not part of the quantity that’s being explored. For example, the picture below shows how we can explore different ways to make 7. This image is in-process and shows the child’s work as they explore how 7 can be made with 6 + 1, 5 + 2, and so on, as in the “Essential Combinations” presentation.

Usage Tips: The control charts are for use by the child to check their work after completing a set of equations to solve. Demonstrate how to find a given problem on the chart and how to read it.

At the end of work with the strip board, always return the strips to their boxes and organize them by color so that they are ready for use next time.