How to Use a Number Line to Add Signed Numbers

Positive and negative numbers, called integers, are a never-ending source of frustration for the students to whom they are being introduced, as well as the teachers who are making the introduction. With a little preparation, and a few easy-to-obtain materials, the introduction can be less painful for everyone involved. Incorporating kinesthetic learning techniques, a hands-on approach, deepens learning for even the least confident students. Start with a simple expression, 6 + -3 = ?

Difficulty: Easy

Instructions

Things You'll Need:

• Paper number line
• LEGO men

1. Lay your paper number line out in front of you. This is a helpful tool, and can be used for other lessons. Use clear packing tape to cover the paper completely, which will prolong the readability of the number line.

2. Assemble a LEGO man to use as your jumper. He always uses the first number in the expression as the starting point. Place him on the number six on the positive part of the number line.

3. Make sure your LEGO man is facing to the right end of the number line. The sign in the expression, in this case a plus sign, determines which way the figure should face. For addition problems, the figure should face toward the right end of the number line. In a subtraction problem, the figure would face left.

4. Decide how the LEGO man will move. Because you are adding a negative three, he will jump backwards (opposite the direction the figure is facing), by three spaces. If you were adding a positive three, he would move forward three spaces. The sign on the second addend determines whether the figure jumps forward or back. Since the figure is on six, and facing right, three jumps backwards places him on three. 6 + -3 = 3.

5. Practice this technique several times with lots of different number sentences. Use a calculator to check your answers. Once you have practiced this method, try using just your finger instead of a LEGO man. Eventually, you'll be able to do this operation, even without the number line.

Tips & Warnings

• Teachers: Consider letting students use this technique on assessments until they are comfortable. It's a very visual way to determine if they understand the concept involved.

References

• Math.com: Adding and Subtracting Integers

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