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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This lesson continues to discuss volume. Students will focus on finding 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.

You can explain how this works using several examples. Test students’ understanding by having them create their own rectangular prisms. They can then work with a partner to find the volume of each other’s figures. The lesson itself is very simple. You can be creative in how you present the concept of adding volumes. You may even want to use real-world examples and have them bring boxes from home.

What Volume as Additive includes

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.


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.

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.