# Addition and Subtraction Within 100

Students investigate addition and subtraction strategies for two-digit numbers ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)). You will add and subtract numbers up to 100, and check your work using inverse operations ([Details](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)).

## Exercises

1. Add these numbers. Show your work on the lines below.

 23 + 15 = ______
 
 _______________________________________________

2. Subtract. Then use addition to check your answer.

 48 − 12 = ______
 
 Check: ______ + 12 = 48

3. Fill in the missing number.

 17 + ______ = 42

4. Add in any order. Which way is easier for you? Circle it.

 A) 5 + 18 + 5 = ______
 
 B) 5 + 5 + 18 = ______

5. Solve this problem.

 Maya has 24 stickers. Her friend gives her 13 more. How many stickers does Maya have now?
 
 ______ stickers

6. Match each subtraction problem to the addition problem that checks it.

| Subtraction | Addition |
|---|---|
| 56 − 20 = 36 | A) 20 + 36 = 56 |
| 75 − 13 = 62 | B) 13 + 62 = 75 |
| 41 − 10 = 31 | C) 10 + 31 = 41 |

## Answer Key

1. 38 (Answers showing breaking apart 23 + 15 as 20 + 3 + 10 + 5, or similar strategy, are correct.)

2. 36; Check: 36 + 12 = 48

3. 25

4. Both equal 28. (B is easier for many students because it groups the 5s together, but either method is correct.)

5. 37 stickers

6. 56 − 20 = 36 matches A; 75 − 13 = 62 matches B; 41 − 10 = 31 matches C

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*AILI homework sheet · language en · model claude-haiku-4-5-20251001 · generated 2026-09-17 · id 49054e48-e5fc-4e89-810c-6da7929ab47b*

### 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/29820)
- node:n2: How can addition and subtraction be interpreted? (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29843)
- node:n3: Students investigate addition and subtraction within 100. (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29844)
- node:n4: Details (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/29846)