Learning how to measure objects using a ruler is a second grade, Common Core math skill: 2.MD.1. Below we show two videos that demonstrate this standard. Then, we provide a breakdown of the specific steps in the videos to help you teach your class.

**Prior Learnings**

Your students will have learned how to measure objects through non-standard units, like using paperclips to measure a pencil (1.MD.1). They should also be able to compare objects using terms like longer, shorter, longest, and shortest (1.MD.2).

**Future Learnings**

In the future, understanding how to measure objects with a ruler will help your students expand on and apply the concept elsewhere. Students will be able to make a line plot, measure objects, and place those measurements on the plot (2.MD.9). Your students will also be able to use rulers marked with halves and fourths of an inch (3.MD.3) and apply “linear measurement to measure perimeter and area” (3.MD.5- 8).

**Common Core Standard: 2.MD.1 - Measure the length of an object by selecting and using appropriate tools: rulers, yardsticks, meter sticks, and measuring tapes**

Students who understand this principle can:

- Find zero on a measuring tool and explain how to use zero when measuring an object.
- Understand that numbers on a measurement tool are spaced equally.
- Identify that an object’s length is the number of equally spaced units and cannot have any overlaps or gaps
- Choose the correct tools to measure objects.
- Explain why specific measurement tools are best for different situations.

**2 Videos to Help You Teach Common Core Standard: 2.MD.1**

Below we provide and breakdown two videos to help you teach your students this standard.

**Video 1: Measuring with Centimeters**

The video begins by explaining that you can measure the length of objects using tools, such as a ruler. The ruler in the video uses centimeters to measure the length of various objects.

First, the video explains how to read the ruler.

- Each space on the ruler is 1 centimeter long.
- The numbers indicate how many spaces a point is away from 0.
- For example, the 6 is six spaces away from 0.
- To find an object’s length, you find how many spaces it covers or how many centimeters long it is.

The first example is of a pencil. When one end of the pencil is aligned with 0, you can see that the pencil is 7 centimeters long. It then asks viewers if they can still measure the pencil with a broken ruler.

- The broken ruler starts at 3.
- The end of the pencil is aligned with 3 and ends at 10.

a. But the pencil is not 10 centimeters long. - The video counts the spaces and finds that the pencil is 7 cm long.
- Students can also find the difference between the two numbers the pencil starts and ends at.
- 10 - 3 = 7

a. When the pencil started at 0, the difference between the two numbers was also 7: (7 - 0 = 7).

The video shows another example demonstrating the difference method discovered above: One way to find the length of an object is to align it with two numbers on a ruler and find the difference.

- The viewers are asked to find the length of a key.
- One end lines up with 6, and the other end lines up with 9.

a. 9 - 6 = 3. - The key is then aligned to start at 0, to check if the above measurement is correct.
- One end lines up with 0, and the other end lines up with 3.

a. 3 - 0 = 3. - The key is 3 cm long.

**Video 2: Measuring Fabric and Objects**

The video starts by explaining how a ruler works. A ruler has two different sides: inches (in) and centimeters (cm). The video practices using inches first by helping out Nora who wants to make clothes for her doll.

- Nora needs to cut the right length of fabric.
- Nora needs an 8 in piece of pink fabric for a skirt.
- To measure 8 in, the 0 on the ruler is aligned with the left edge.

a. The cloth is cut at the 8 in mark. - The same method is used to measure the other fabrics.

a. 2 inches of blue fabric for a ribbon.

b. 5 inches of purple fabric for a blouse.

c. 10 inches of red fabric for a scarf.

The video then provides examples for using centimeters, stating that the centimeters side works the same way as the inches side. The viewers are then asked how long some objects are in centimeters.

- The left edge of a comb is aligned with 0, and the right edge ends at 10.

a. The comb is 10 cm. - The left end of a phone is aligned with 0, and the right edge ends at 13.

a. The phone is 13 cm. - The left end of a letter is aligned with 0, and the right edge ends at 11.

a. The letter is 11 cm.

**Want more practice?**

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*Information on standards is gathered from The New Mexico Public Education Department's New Mexico Instructional Scope for Mathematics and the Common Core website.