# Adding and Subtracting to 100 *Grade 2 Math: playing with numbers up to 100* ## Slide 1: Adding and Subtracting to 100 ![Adding and Subtracting to 100](https://goa-cc-uat-aili-app-001.azurewebsites.net/api/generate/e2260aaf-8e3a-4f22-a968-769429750c88/asset/799) *Grade 2 Math: playing with numbers up to 100* *Sources: [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)* > Notes: Learning intention: We are learning to add and subtract numbers up to 100. Success criteria: I can add two-digit numbers, subtract two-digit numbers, and check my answer. Materials: base-ten blocks, number lines, whiteboards. Time: 5 minutes to introduce and set purpose. ## Slide 2: What Are We Learning? - We add numbers to make a sum up to 100. - We subtract numbers starting from up to 100. - A sum can be made in many different ways. - We check our answers using the opposite operation. *Sources: [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844), [Understanding](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29847), [Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852)* > Notes: Learning intention: understand the goal of the unit. Success criteria: students can restate what addition and subtraction mean in their own words. Formative checkpoint: ask a volunteer to explain 'sum' and 'difference' using fingers or counters. Support: use physical counters for concrete demonstration. Extension: ask students to give an example sum equal to 100. ## Slide 3: Strategies We Can Use - **Making tens**: Group numbers to make friendly tens, like 8 + 2 = 10. - **Using doubles**: Use known doubles, like 6 + 6, to help with harder facts. - **Number facts to 10**: Recall facts like 4 + 5 = 9 quickly, without counting. - **Checking with inverse**: Use subtraction to check an addition answer, and the reverse. *Sources: [Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29850), [Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852), [Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852), [Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29850)* > Notes: Learning intention: explore strategies for two-digit addition and subtraction. Success criteria: students can name and use at least one strategy. Materials: hundred chart, ten-frames. Formative checkpoint: exit slip asking students to solve one problem and name their strategy. Support: pair students with a hundred chart for counting support. Extension: challenge students to solve 47 + 36 using two different strategies. ## Slide 4: Building 100 with Tens 1. **Start with 0**: We begin counting from zero. 2. **Add groups of 10**: Count 10, 20, 30, all the way to 100. 3. **Mix tens and ones**: See 100 as 7 tens and 3 tens, or other combinations. 4. **Add more addends**: Combine three or more numbers, order does not change the sum. *Sources: [Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846), [Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29848), [Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29848), [Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)* > Notes: Learning intention: visualize 100 as made of tens in different ways. Success criteria: students can show two different ways to build 100 using tens. Materials: base-ten rods, hundred chart. Formative checkpoint: have students build 100 with blocks in two different combinations. Support: start with building 50 first. Extension: build 100 with three or more addends and explain the associative property. ## Slide 5: Solving a Real Problem A garden has 100 flower spots. 64 spots have flowers already. How many spots are still empty? We can find the missing number using addition or subtraction. We can also use addition and subtraction to compare lengths, like how much longer one ribbon is than another. > Missing numbers and measuring lengths A garden has 100 flower spots. 64 spots have flowers already. How many spots are still empty? We can find the missing number using addition or subtraction. We can also use addition and subtraction to compare lengths, like how much longer one ribbon is than another. *Sources: [Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852), [Understanding](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29851), [Understanding](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29851)* > Notes: Learning intention: apply addition and subtraction to solve problems with countable quantities and lengths. Success criteria: students can solve a missing-number problem and explain their thinking. Materials: counters, measuring strips, whiteboards. Formative checkpoint: circulate and check student strategies on the garden problem. Support: use counters to model the 100 spots directly. Extension: create their own missing-number story problem for a partner to solve. ## Slide 6: Great Math Thinking Today! **Summary:** We explored addition and subtraction within 100, we saw 100 as groups of tens, we used strategies like making tens and doubles, and we solved problems with missing numbers and lengths. **Question:** Can you show one more way to make 100 using tens and ones? *Sources: [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844), [Understanding](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29847), [Understanding](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29851), [Understanding](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29847)* > Notes: Wrap-up: revisit learning intentions and success criteria as a class. Formative checkpoint: thumbs up, sideways, or down for confidence with today's strategies. Support: provide a hundred chart for the closing question. Extension: ask students to write their own addition equation that equals 100 using three addends. --- *AILI presentation · language en · model claude-sonnet-5 · generated 2026-09-17 · id e2260aaf-8e3a-4f22-a968-769429750c88* ### Sources - node:n1: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29843) - node:n2: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844) - node:n3: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846) - node:n4: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29848) - node:n5: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29847) - node:n6: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29850) - node:n7: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852) - node:n8: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29851) - node:n9: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852) - node:n10: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29850) - node:n11: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29848) - node:n12: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844) - node:n13: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29847) - node:n14: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29851) - node:n15: Mathematics › Mathematics (K–6) › Grade 2 › Number: Quantity is measured with numbers that enable counting, labelling, comparing, and operating. › How can addition and subtraction be interpreted? › Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)