How To Use The Broken Ruler to Measure Your Students’ Measurement Understanding

Measurement worksheets often don’t give us a real assessment of whether or not kids can measure. In this vlog post we are going to look at how to use the broken ruler to measure your students’ measurement understanding.

Watch the video or read the transcript below.

The Biggest Measurement Misconceptions

Do activities like this really tell us whether or not our kids can measure?

One of the hard parts, as we start moving into measuring things with rulers is that before kids have gotten to measurement with rulers we're having them measure with objects. They might be measuring with Unifix cubes, paper clips or any kind of non-standard measurement tool. We use these things to help kids see the actual units because as they move into using rulers, there's no real thing for them to count.

Something you've heard me talk about before is that I really love using a number path instead of a number line and rulers are just like a number line - it is a number line! This means that kids end up looking at the tick marks of the ruler instead of seeing it as the distance. When you're using a ruler it's the distance that we're looking at. Kids have to understand that you're not just counting the tick marks, but the space between.

Our students who are young really struggle with this concept. Because of this, we start out with non-standard units of measure, but when they move into rulers it's still really, really tough. And a lot of the times the types of activities and worksheets that kids have around measurement are like this one.

Problem with this is that everything starts at zero so that all they have to do is just look at the very end of the object, line it up, and say it ends right here so that's how long it is. They don't really have to think of measurement as the space between, they just see it as where does it land on the ruler? This became very prevalent to me when I was reading an article called Picture This: Increasing Math and Science Learning by Improving Spatial Thinking by Nora Newcombe. I was actually reading this article on my computer and I had my son sitting next to me.

This image came up and I thought, "Hmm, I'm gonna check to see how he thinks about this." Take a look at this image and think about how kids might talk about the length or the size of these two bears. What do you think that they would say about these two measurements and these two images?

Let's take a look at what my son said:

[Christina] “How big do you think this bear is?”

[My Son] “Four feet.”

[Christina] “Four feet? And why do you say four feet?”

[My Son] “Because it's at the four.”

[Christina] “What about this other bear down here? What do you think that one is?”

[My Son] “Two feet.”

[Christina] “Two feet? So you think that one's two and that one's four. What one's bigger then?”

[My Son] “The top one.”

[Christina] “The top one, why do you think that's bigger?”

[My Son] “Because that's four feet and the bottom is two feet.”

Do you see the issue here? All that he's looking at is just the last number where it ends. He's not realizing that it didn't even start at zero and that really you're looking at that space, that length of space that the bear takes up. It is not the last amount that it ends at. Many of our students view measurement in that way because we always start at zero with our rulers.

Why It's Time For You To Break Your Ruler

I want to encourage you today to use a broken ruler. That's right, I want you to take out your rulers and break them. You can actually find a ton of broken ruler activities by searching on Google or going to Teachers Pay Teachers and other blogs, one like the image below.

However, I want to caution you to be careful with some of these that you can find on the internet. Take a close look at this image.

Really look at it for a moment. Is there anything in this image that bugs you? There sure are some things bugging me. I don't know if it's the same thing that bugs you, but for me the thing that bugs me the most on this is that it's not proportional. The hammer is basically the same size as a pen. And in real life those are not the same size.

When it comes to measurement, kids really struggle with estimation and knowing how big things are. They have to distinguish if something is almost a foot or is this just a couple of inches? If the images that we have on worksheets are not helping us out, they aren't very useful worksheets. Yes. they could figure out how long that hammer is, but it doesn't relate to real life.

That’s why I want you to get your rulers out and break them. And then have your kids measure everything! Whenever they're doing any kind of measurement, they don't have to start at zero. You don't need a full ruler to be able to do it.

So get your rulers out, break them, and start letting kids measure. Measure everything but let's try it out with a broken ruler to see if kids really understand measurement as that length and not just the last digit that it ends on.