--- title: "Volume as additive" description: "Recognise volume as additive; find volumes of composite solid figures made of two or more non-overlapping right rectangular prisms" canonical: https://lightmysky.com/learn/mathematics/volume-as-additive-mt_5TBUFnCy5- source: https://lightmysky.com/learn/mathematics/volume-as-additive-mt_5TBUFnCy5-.md retrieved: 2026-10-19 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Volume as additive Recognise volume as additive; find volumes of composite solid figures made of two or more non-overlapping right rectangular prisms Subject: Mathematics · Area: Measurement · Ages 10 to 11 Page: https://lightmysky.com/learn/mathematics/volume-as-additive-mt_5TBUFnCy5- ## Ready when they can - Decompose an L-shaped solid into two cuboids and calculate total volume - Solve a real-world problem requiring the volume of a composite figure (e.g. a step-shaped structure) - Explain why splitting a composite solid into rectangular prisms allows calculation of total volume ## Lesson: Volume as additive A composite solid is a shape made from two or more boxes joined together, like an L-shape or a staircase. You already know how to find the volume of one rectangular prism: multiply length, width, and height. For a composite solid, split it into separate prisms first. *(drawing: Box A holds 24 cubic units. Box B holds 20 cubic units. Together they hold 44 cubic units.)* **Example.** An L-shaped pool splits into two rectangular sections. Section 1 is 6 m long, 3 m wide, and 2 m deep: that's 6 x 3 x 2 = 36 cubic meters. Section 2 is 4 m long, 2 m wide, and 2 m deep: that's 4 x 2 x 2 = 16 cubic meters. Total volume: 36 + 16 = 52 cubic meters. **Tip.** Split a composite solid along its natural edges so the pieces don't overlap and don't leave gaps. Then every cubic unit gets counted exactly once. **Recap.** Split a composite solid into rectangular prisms, find each volume, then add them together for the total. ## Practice 18 questions on this page, each with its working shown. ## Needs first - [Addition and subtraction strategies (age 10+)](https://lightmysky.com/learn/mathematics/addition-and-subtraction-strategies-age-10-mt_JH_6RpNWjr) - [Volume of cuboids](https://lightmysky.com/learn/mathematics/volume-of-cuboids-mt_nTL-owFJTF) ## Opens up - [Volume and Surface Area of Prisms and Cylinders](https://lightmysky.com/learn/mathematics/volume-and-surface-area-of-prisms-and-cylinders-mt_JTLJ5LDrYh)