A Hands On Approach to Subtraction on the Number Line

Number lines are a great visual tool for understanding numbers and operations. However, students often don’t like using them. Today we are going to look at how to make the number line hands on, so students grasp the concept of a number line and hopefully see what a great tool it can be.

Concrete

Let’s look at an example word problem a 2nd grade might face. Lucas did 27 jumping jacks. Julian did 46 jumping jacks. How many more jumping jacks did Julian do?

An open number line is often used to show students subtraction strategies. I love using an open number line but we need concrete approach before jumping right to that visual model.

Have students represent 46 and 27 using Base 10 blocks but instead of grouping the tens and ones in a pile, have students make a long train for each number. In this problem we want to see how many more jumping jacks Julian did, so we want to think 27 + ? = 46? If you have a different colored Base 10 block, it is helpful for students to see the difference in another color. Have students line up Base 10 blocks until the two number are the same length.

How many did we have to add to reach 46? 19! Therefore, 46 – 27 = 19.

Representational

Once students are comfortable solving the number line with Base 10 blocks, show students how this long line we made is really a number line! The same problem can be modeled on a number line.

Abstract

I suggest giving students a number line with tick marks first. Seeing the individual numbers make the concept more manageable for students. Once they have mastered the number line with tick marks, they are ready for the open number line!