##
* *Reflection: Checks for Understanding
Perimeter of my fence - Section 2: Independent Practice

The student in this video Finding the Perimeter is measuring in centimeters but he consistently places the ruler with the inches side next to what he is measuring and then tries to read the centimeter side of the ruler. I keep trying to help him slide the ruler down so he is actually measuring with the centimeter edge. I want him to learn to use the tool (the ruler) correctly (MP5). He is measuring with centimeters as the instructions said, but he is trying to do it across the ruler. He has a hard time understanding why I keep sliding the ruler down so that the centimeter edge is next to the line he is measuring.

The student measures all the sides and creates a Tens and Ones house to add his numbers. He records all the 2 digit numbers correctly but then when the last line is only 6 centimeters long, he records it as 6 tens. I have to ask him if he just measured 6 tens or 6 ones. Here he is learning that attending to where he puts the numbers will make a difference in the answer. Place value is important and he must be careful to think about place value even when he is measuring (MP6).

He shows some understanding of place value in the way he writes the numbers and then when he is adding, he adds the tens first and finds 3 tens, but when he has 12 ( which he realizes with my help should be 14 ones), he quickly changes the 3 tens to 4 tens, showing that he knows that he needs to move the tens into the tens column.

*Checks for Understanding: Using The Ruler Appropriately*

# Perimeter of my fence

Lesson 2 of 6

## Objective: SWBAT discuss the word perimeter and measure several shapes to determine which is the largest

## Big Idea: A farmer needs a fence to keep the bunny out of his lettuce patch, but does he understand how to buy the right amount?

*50 minutes*

#### Teaching the Lesson

*15 min*

Today I use a short video to introduce the idea of perimeter. I have a farmer who tries to grow lettuce but a very smart bunny keeps eating the lettuce. The farmer is told to build a fence, but he only builds the fence on one side of the lettuce patch. He eventually finds out that he has to build a fence all the way around (the perimeter of his field.)

I show the video and we talk about what the farmer learned. I ask if anyone can tell me what the word perimeter means now that they have seen the farmer? I make sure that students have a grasp of the term before moving to the next part of the lesson.

#### Resources

*expand content*

#### Independent Practice

*25 min*

I have drawn a page shapes document.pdf with a number of different shapes. I ask students to find the perimeter of each shape by measuring in centimeters. We discuss how we might add the 3 or more sides of a figure using an addition strategy that we are familiar with. Students may suggest using tens frames, tens and ones houses, number lines, etc. We reinforce that there are several ways to find the answer.

I have each student work independently and I circulate around to help students who are having difficulty with the process of measuring and then adding more than 2 numbers.

#### Resources

*expand content*

#### Closing

*10 min*

At the end of the lesson I call students to the rug with their perimeter papers. I display one of the figures and ask for a student to tell us what he/she found as the perimeter. I ask other students if they agree. We realize that because we were each measuring and some of the figures were not exactly on the centimeter line, one person might say it was closer to one number, and one to the other. This would change our results just a little. I explain to students that we want to be as careful as possible to start at the zero point of our ruler, but when a line is not exact, we have a choice as to which centimeter we think is the closest. I want students to be precise in their measurements (MP6), but we have not yet worked with quarters of a centimeter so students will move to the nearest full centimeter.

If there is a big difference, I ask for 2 students to tell us the measurements they got for each side and then together we add them up using one of the strategies a student suggests. We may find that a student measured a side in inches by mistake, or that they placed a number incorrectly in the tens or ones place which gave the different result.

Working together we check 2 of the figures and that gives students a sense of how they may have done with the idea of finding perimeter. It also allows for students to correct their own misunderstandings.

*expand content*

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- UNIT 1: What and Where is Math?
- UNIT 2: Adding and Subtracting the Basics
- UNIT 3: Sensible Numbers
- UNIT 4: Sensible Numbers
- UNIT 5: Everything In Its Place
- UNIT 6: Everything in Its Place
- UNIT 7: Place Value
- UNIT 8: Numbers Have Patterns
- UNIT 9: Fractions
- UNIT 10: Money
- UNIT 11: The Numbers Are Getting Bigger
- UNIT 12: More Complex Numbers and Operations
- UNIT 13: Area, Perimeter and More Measurement
- UNIT 14: Length
- UNIT 15: Geometry
- UNIT 16: Getting Ready to Multiply
- UNIT 17: Getting Better at Addition and Subtraction
- UNIT 18: Strategies That Work