# Adding and Subtracting to 100 *30 minutes, 3 stages* You are learning how to add and subtract numbers up to 100 ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)). Knowing your number facts helps you solve bigger problems faster ([Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29850)). Today you will practice facts, try two-digit problems, and solve a story problem. ## Stage 1: Warm-up (8 min) Students investigate addition and subtraction within 100, including how sums can be composed in multiple ways and how the order in which more than two numbers are added does not affect the sum. First, solve these facts from memory. Write just the answers. 1. 6 + 7 = 2. 9 + 5 = 3. 8 + 8 = 4. 13 − 6 = 5. 12 − 5 = 6. 16 − 8 = Knowing facts like these helps you add bigger numbers ([Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29850)). Now try this one with three numbers. Add them in any order you like. The order does not change the answer ([Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)). 7. 4 + 6 + 8 = ____ Check: did you get 18 no matter which two numbers you added first? Try it a different order to prove it. ## Stage 2: Two-digit practice (12 min) Now solve these two-digit problems ([Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852)). You can use a strategy like making a ten, or drawing tens and ones blocks (, [Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29850)). 1. 24 + 35 = 2. 47 + 26 = 3. 58 − 23 = 4. 82 − 47 = 5. 36 + 29 = Pick one problem above. Draw base-10 blocks (long lines for tens, small squares for ones) to show how you got your answer. Now find the missing number: 6. 40 + ____ = 100 7. 100 − ____ = 65 Think of 100 as groups of ten. How many tens make 100? ([Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29848)) ## Stage 3: Story problem (10 min) Read this problem and solve it. Ben has 47 stickers. His sister gives him 28 more. How many stickers does Ben have now? Write a number sentence and solve it. Then draw or write how you checked your answer using the opposite operation ([Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852)). Now try this one: A ribbon is 100 centimeters long. Mia cuts off 36 centimeters. How much ribbon is left? Solve it, and write one sentence explaining your strategy. ## Self-check 1. Look at problem 24 + 35 from Stage 2. Use subtraction to check your answer. Does it work? ([Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29852)) 2. Can you think of two different ways to make the sum 100 using multiples of ten? Write both ways. ([Skills](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29848), [Understanding](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29847)) 3. In your own words, what does it mean to "regroup" when adding two-digit numbers? ([Knowledge](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29850)) --- *AILI student homework · language en · model claude-sonnet-5 · generated 2026-09-17 · id 76a3c6f6-2c68-4949-ba09-929529e9b5a5* ### 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) - resource:r1: Resources › type#activity, type#classroomactivity › MAT2, MAT3, MAT4, MAT5 (https://goa-cc-uat-aili-app-001.azurewebsites.net/library/resource/zcsdujXlaUa2uuq1-kBv0Q)