Volume as Additive


Volume as Additive is designed for 5th grade students. The lesson continues instruction on volume and finding volume of irregular objects. This lesson focuses on irregular rectangular prisms. Students will learn how to divide a figure into two separate prisms. After finding the volume of each separately, then they can add the two sums to get the full volume. They will also learn that a figure can be divided in multiple ways.

This lesson is fairly brief. You can get creative with how to illustrate the concept to your class. One suggestion is to have some students add volumes in front of the class. You can ask questions along the way, such as why this is possible with multiple shapes. And instead of using snap cubes, you could have students bring boxes from home.

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What our Volume as Additive lesson plan includes

Lesson Objectives and Overview: Volume as Additive teaches students how to find the volume of irregular solid figures that are rectangular. They will break the figure into two separate rectangular prisms. Using their knowledge of volume, they will find the volume of each prism. Then they will add the two sums to determine the volume of the full figure. This introduces the concept of volume as additive. This lesson builds on what the students have already learned about volume. After reviewing the volume formula, they can practice this new concept. The activity, practice, and homework worksheets provide extra practice for the students. They will be able to work with each other to further solidify their comprehension of the material. This lesson is for students in the 5th grade.

Classroom Procedure

Every lesson plan provides you with a classroom procedure page that outlines a step-by-step guide to follow. You do not have to follow the guide exactly. The guide helps you organize the lesson and details when to hand out worksheets. It also lists information in the orange box that you might find useful. You will find the lesson objectives, state standards, and number of class sessions the lesson should take to complete in this area. In addition, it describes the supplies you will need as well as what and how you need to prepare beforehand. The only supplies you will need for this lesson are snap cubes. To prepare for this lesson ahead of time, you can gather the snap cubes and copy the handouts.

Options for Lesson

Included with this lesson is an “Options for Lesson” section that lists a number of suggestions for activities to add to the lesson or substitutions for the ones already in the lesson. One optional addition to the activity is to let two or more students add their volumes together while the class watches and asks questions about how the process works with more than two shapes. As an additional activity, you could have students build rectangular prisms and measure them instead of using snap cubes. Finally, you can have students bring in boxes from home as a figure for volume.

Teacher Notes

The teacher notes page includes a paragraph with additional guidelines and things to think about as you begin to plan your lesson. This page also includes lines that you can use to add your own notes as you’re preparing for this lesson.


Volume as Additive

The Volume as Additive lesson plan includes two pages of content. The lesson begins by defining volume as the amount of space it takes to fill the inside of a solid figure. If you want to find the volume of a rectangular prism, you need to multiply the length by the width by the height. If the shape is irregular, you should break the shape into multiple rectangles, find the area of each, and add them together to get the total volume. The lesson illustrates a few examples of this. The lesson shows you how to break the same irregular figure up in multiple ways, illustrating that you get the same answer no matter how you break it up. This is what we mean when we say that volume is additive. You can find the volume of two shapes and add them together to find the sum total of the volume.


The Volume as Additive lesson plan includes three worksheets: an activity worksheet, a practice worksheet, and a homework assignment. You can refer to the guide on the classroom procedure page to determine when to hand out each worksheet.


Students will have to work with their classmates on the activity. This provides an opportunity for you to gauge who may need extra help. The students will create a prism with snap cubes. After that, they will have to draw their figure on the page. Next, they will take their prism to four different classmates. With each classmate, they will add the sum of both of their prisms. The sheet provides four boxes where they can record their answers.


The practice worksheet illustrates that irregular figures can be divided in multiple ways. The sheet shows two sets of identical rectangular prisms. The students will divide each figure into two separate prisms in two different ways. Then they will find the volume of each to prove that they are the same.


The homework assignment provides further practice with volume. There are five total figures on the page. Each differs a little in presentation. Some look like snap cubes set up in a rectangular prism. On the other hand, some have only the outline with the measurements. This will test students’ ability to use different techniques to solve the problem.

Worksheet Answer Keys

This lesson plan includes answer keys for the practice worksheet and the homework assignment. If you choose to administer the lesson pages to your students via PDF, you will need to save a new file that omits these pages. Otherwise, you can simply print out the applicable pages and keep these as reference for yourself when grading assignments.

Additional information


5th Grade



State Educational Standards


Lessons are aligned to meet the education objectives and goals of most states. For more information on your state objectives, contact your local Board of Education or Department of Education in your state.

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Love the information provided

United States United States

Volume as Additive is perfect!

Loved it! My students enjoyed the challenge and it made my teaching much easier! Thank you!!