--- title: "Adding and subtracting fractions with the same bottom number within one whole" description: "Add and subtract fractions with the same denominator within one whole (e.g. 5/7 + 1/7 = 6/7)" canonical: https://lightmysky.com/learn/mathematics/adding-and-subtracting-fractions-with-the-same-bottom-number-within-one-whole-mt_a1FdAsRKOF source: https://lightmysky.com/learn/mathematics/adding-and-subtracting-fractions-with-the-same-bottom-number-within-one-whole-mt_a1FdAsRKOF.md retrieved: 2026-09-12 --- > **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`. # Adding and subtracting fractions with the same bottom number within one whole Add and subtract fractions with the same denominator within one whole (e.g. 5/7 + 1/7 = 6/7) Subject: Mathematics · Area: Fractions · Ages 7 to 8 Page: https://lightmysky.com/learn/mathematics/adding-and-subtracting-fractions-with-the-same-bottom-number-within-one-whole-mt_a1FdAsRKOF ## Ready when they can - Calculate 2/5 + 2/5 = 4/5 - Calculate 6/8 − 3/8 = 3/8 - Explain that when denominators are the same, you add/subtract the numerators ## Lesson: When the Bottom Numbers Match A fraction has two numbers. The bottom number tells how many equal parts make one whole. The top number tells how many of those parts you have. When two fractions have the same bottom number, adding or subtracting them is easy. Just add or subtract the top numbers. The bottom number stays exactly the same. *(drawing: This bar is cut into 5 equal parts. 2 of them are shaded, so this shows 2/5.)* **Example.** Ravi eats 2/5 of a pizza at lunch. Later he eats another 2/5 of a same-size pizza. Both fractions have a bottom number of 5, so he just adds the top numbers: 2 + 2 = 4. Ravi ate 4/5 of a pizza in total. **Tip.** Never add or subtract the bottom numbers. Only the top numbers change. 2/5 + 2/5 is 4/5, not 4/10. **Recap.** Same bottom number? Just add or subtract the top numbers, and keep the bottom number the same. ## Practice 17 questions on this page, each with its working shown. ## Needs first - [Fractions on a number line](https://lightmysky.com/learn/mathematics/fractions-on-a-number-line-mt_Kr3IyA6m-O) - [Addition as combining or putting together two](https://lightmysky.com/learn/mathematics/addition-as-combining-or-putting-together-two-mt_OvyoRo47K-) ## Opens up - [Adding Fractions (Same Denominator)](https://lightmysky.com/learn/mathematics/adding-fractions-same-denominator-mt_CBHwluE6Lp) - [Precision in mathematical language and notation](https://lightmysky.com/learn/mathematics/precision-in-mathematical-language-and-notation-mt_HY8Yycu_rz) - [Solving problems with fractions (age 7+)](https://lightmysky.com/learn/mathematics/solving-problems-with-fractions-age-7-mt_SsLWS_APM7)