# Addition and Subtraction Within 100 *A Grade 2 math adventure with tens and ones* ## Slide 1: Addition and Subtraction Within 100 ![Addition and Subtraction Within 100](https://goa-cc-uat-aili-app-001.azurewebsites.net/api/generate/1d3d5331-39fb-4526-b553-e920be39f99b/asset/2008) *A Grade 2 math adventure with tens and ones* *Sources: [Guiding question](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29843), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)* > Notes: Introduce the topic. Learning outcome: students investigate addition and subtraction within 100 ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)). Guiding question: how can addition and subtraction be interpreted ([Guiding question](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29843))? Ask students to share what they already know about adding two-digit numbers. ## Slide 2: What We Will Learn - We will add numbers up to 100 ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)). - We will subtract numbers up to 100 ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)). - We will find missing numbers in a sum or difference ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). - We will check our answers with a different operation ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). - We will use tens facts we already know to help us ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). *Sources: [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844), [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)* > Notes: Success criteria for the lesson block: I can add two-digit numbers to make a sum up to 100. I can subtract two-digit numbers with a minuend up to 100. I can use inverse operations to check my work ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). Formative checkpoint: students investigate addition and subtraction within 100. ## Slide 3: A Strategy for Adding Two-Digit Numbers 1. **Look at the tens**: Add the tens together first, like 30 plus 20 ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). 2. **Look at the ones**: Add the ones together, like 4 plus 3 ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). 3. **Make a ten if you can**: If the ones make 10 or more, trade for a new ten ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). 4. **Put it together**: Join the tens and ones to find the sum ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). *Sources: [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846), [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759), [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29925)* > Notes: Materials: base-ten blocks or a hundred chart, whiteboard. Model with 34 + 23 using blocks. This links to strategies from Grade 1 like making tens ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759)) and prepares students for Grade 3 place value algorithms ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29925)). Checkpoint: have pairs solve 45 + 32 on whiteboards and show their tens-and-ones thinking. ## Slide 4: Addition and Subtraction Are Connected **Fact Families** Addition facts have matching subtraction facts ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759)). If we know 6 plus 4 equals 10, we also know 10 minus 4 equals 6 ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759)). These related facts form a fact family. **Checking Our Work** We can check a sum by subtracting one addend back ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). We can check a difference by adding it back to the number we subtracted ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). This uses inverse operations. *Sources: [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759), [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)* > Notes: Review Grade 1 fact family knowledge before extending to two-digit numbers ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759)). Skill practice: students apply the associative property of addition, recognizing that the order in which more than two numbers are added does not affect the sum([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). Support: provide a fact family triangle for smaller numbers first. Extension: ask students to build a fact family for a two-digit sum like 45 and 32. ## Slide 5: Ways to Solve a Problem - **Combine parts**: Put two groups together to find the whole ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759)). - **Take away**: Remove part of a quantity from the whole ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759)). - **Compare**: Find how much bigger or smaller one group is ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759)). - Missing number: find the unknown part when the whole and one part are known, using a related subtraction fact. *Sources: [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759), [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)* > Notes: These problem types build on Grade 1 contexts for addition and subtraction ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759)) and extend into finding a missing quantity within 100 ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). Differentiation: support students with counters and a number line; extension students try two-step word problems within 100. Formative checkpoint: exit ticket with one word problem per type. ## Slide 6: Great Work With Numbers to 100! **Summary:** We practiced adding and subtracting numbers up to 100 ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)). We learned that the order in which more than two numbers are added does not affect the sum([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). Students apply strategies for addition and subtraction within 1000([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29923)). **Question:** Can you make up your own addition problem that adds up to exactly 100? *Sources: [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844), [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29923), [Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29925)* > Notes: Wrap up by connecting to Grade 3 learning, where students apply standard algorithms for addition and subtraction within 1000 ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29923)), ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29925)). Use the closing question as an exit ticket or partner talk activity. --- *AILI presentation · language en · model claude-sonnet-5 · generated 2026-09-17 · id 1d3d5331-39fb-4526-b553-e920be39f99b* ### Sources - node:n1: Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29733) - node:n2: How can addition and subtraction provide perspectives of number? (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29756) - node:n3: Students examine addition and subtraction within 20. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29757) - node:n4: Details (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29759) - node:n5: Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29820) - node:n6: How can addition and subtraction be interpreted? (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29843) - node:n7: Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844) - node:n8: Details (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846) - node:n9: Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29915) - node:n10: How can processes be established for addition and subtraction? (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29922) - node:n11: Students apply strategies for addition and subtraction within 1000. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29923) - node:n12: Details (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29925)