Well…it’s time to start thinking about upcoming units in my fourth grade studio–and I wanted to share with you something I have been doing more and more of this year with great results. I challenge you to think about how you can incorporate this simple strategy into your math instruction over the upcoming months.

### Number Sense and Number Lines

As you all know, number sense is critical for students as we work to develop well rounded mathematical thinkers. It isn’t enough to be able to DO math, students need to be able to UNDERSTAND math, to reason about math, to talk about math, to explain about math, and to be able to apply math. One thing that I have noticed is that my fourth graders (even my mathematically best and brightest) are very computation based. They quickly learn algorithms and solve problems but sometimes the trickiest questions trip them up. consider the following number line I presented to my students earlier this year.

My question–“What number would go by the blue line?” Trust me, I truly thought this was an easy one…a “no brainer”…a “warm up”. What happened was astonishing! My students (especially the mathematically best and brightest!) all started yelping about how easy it was, blah blah blah. When I asked for the answer, I got the following:

**It’s so easy! It’s 2,000 because 5,000 – 1,000 is 4,000 so you take half of that!**

**It’s so easy! It’s 2,500 because the number line goes to 5,000 and the blue line is halfway!**

Fascinating, right? So…needless to say…we changed our course for the day and tackled number lines and thinking about numbers. We created all sorts of similar number lines…we changed the starting and ending numbers, we changed the “blue line”, we tried fractions and decimal, we tried adding in negative numbers. Most importantly, we LOOKED CLOSER (see earlier post!!!) and really started paying attention to number lines. We have amazing discussions–truly amazing discussions, and I am convinced many of my students are changed because of it. We have continued to work regularly with number lines, and I can honestly say that simple problem has dramatically deepened students’ mathematical understanding.

### Rigorous math thinking

So…my challenge to you is this: How can YOU incorporate number lines into what you teach in math? What other ways can you use them? I actually use number lines as exit slips…I give problems similar to the one above and ask students to explain their thinking. I’ll even give problems as open ended as “Design a number line that accurately shows me where 0.35 and 2.5 would be. Explain your thinking.” Another favorite–have students build a number line with a “mystery blue line” and exchange it with a partner. Have the partner write the missing number and explain their thought processes. The two students need to come to an agreement about what number should be there.

(NOTE: Try these problems with your teacher friends…you can learn a LOT about their own mathematical understanding! We had a teacher who had her eyes really opened about number sense when we tried these at our team time!)

Check out this kiddo finding “equal parts” on a number line moving from 0 to 1.

Are you interested in using some of the number line resources I have in my store? Here are a few resources that might help you dig into improving your students’ place value understanding. The 0 – 120 resource is perfect for late first grade and ideal for second grade, but I use it every year with an intervention group and to warm up my whole class of fourth graders because even though many may “know” their numbers to 120, their true understanding of place value is not strong enough. See what YOU think!