--- title: "Decimals to three places" description: "Solve problems involving numbers with up to three decimal places" canonical: https://lightmysky.com/learn/mathematics/decimals-to-three-places-mt_sA2OvTiech source: https://lightmysky.com/learn/mathematics/decimals-to-three-places-mt_sA2OvTiech.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`. # Decimals to three places Solve problems involving numbers with up to three decimal places Subject: Mathematics · Area: Fractions · Ages 9 to 10 Page: https://lightmysky.com/learn/mathematics/decimals-to-three-places-mt_sA2OvTiech ## Ready when they can - Calculate the total of three measurements: 1.234 m + 0.567 m + 2.199 m - A bottle holds 1.5 litres and 0.375 l is poured out. How much remains? - Find two numbers with 3 d.p. that add to make 1 ## Lesson: Working with three decimal places Numbers like 1.234 have three digits after the decimal point: tenths, hundredths, and thousandths. You already know how to compare these numbers. Now you'll add and subtract them, just like whole numbers, but the decimal points must line up first. As with whole numbers, 10 of one place make 1 of the next place to the left: 10 thousandths make 1 hundredth, and 10 hundredths make 1 tenth. That is what lets you carry and regroup. *(drawing: Write 2.4 as 2.400, subtract 0.615, and 1.785 is left.)* **Example.** Add 0.755 m, 1.230 m, and 2.015 m. Line up the decimal points so tenths sit under tenths, hundredths under hundredths, and thousandths under thousandths. Adding column by column gives exactly 4.000 m. **Example.** Work out 2.4 - 0.615. Write 2.4 as 2.400 so every column lines up. Regroup: 2.400 becomes 1 one, 13 tenths, 9 hundredths and 10 thousandths. Now subtract each column: 10 - 5 = 5 thousandths, 9 - 1 = 8 hundredths, 13 - 6 = 7 tenths, and 1 - 0 = 1 one. The answer is 1.785. To find a missing part, subtract. What goes with 0.280 to make exactly 1? Write 1 as 1.000 and take away 0.280: 1.000 - 0.280 = 0.720. Then check by adding: 0.280 + 0.720 = 1.000. **Recap.** Line up the decimal points, padding with zeros if needed, then add or subtract column by column. ## Practice 16 questions on this page, each with its working shown. ## Needs first - [Comparing Decimals](https://lightmysky.com/learn/mathematics/comparing-decimals-mt_933BohS9BH) - [Rounding decimals (age 9+)](https://lightmysky.com/learn/mathematics/rounding-decimals-age-9-mt_Ii1hV4V5ql) ## Opens up - [Rounding to a required degree of accuracy](https://lightmysky.com/learn/mathematics/rounding-to-a-required-degree-of-accuracy-mt__casygEB85)