Addition and Subtraction within 20: Fluency and Problem Solving
Free sample questions, a clear explanation, and 5 practice skills with an AI tutor that guides without giving the answer away.
Math Explorer: Your Superpower to 20!
Hello, Superstar! Think about your favorite snacks. When you get more snacks for your lunchbox, that's addition! When you share some with a friend, that's subtraction. You use these math superpowers every day! Now, let's practice using them with all the numbers up to 20 to make you a super-fast problem solver.
Our Secret Strategy: Make a 10!
Working with the number 10 is easy and fun! We can use it to solve bigger problems in a snap. It's like building a bridge to the right answer.
- Adding 8 + 6: Let's help 8 get to 10. It needs 2 more! We can borrow 2 from the 6. Now our problem is 10 + 4. That’s so much easier—it’s 14!
- Subtracting 15 - 7: Let's jump back to 10 first. From 15, we take away 5 to get to 10. We still need to take away 2 more (because 5 + 2 = 7). Now our problem is 10 - 2. The answer is 8!
Solving Math Mysteries with Bar Models
Sometimes, a number is missing in our equation, like 9 + ? = 16. It's a mystery! To solve it, we can draw a picture called a bar model. It helps us see the whole story. The big bar is the "whole" (16), and it's made of two "parts" (9 and our mystery number). By looking at our drawing, we can see that the whole (16) minus the part we know (9) will give us the missing part. The mystery number is 7!
Now, You're the Math Storyteller!
The most exciting part of being a Math Explorer is creating your own adventures! Try making a word problem about your toys, pets, or friends. For example: "Leo had 11 crayons. He lost some. Now he has 8. How many did he lose?" You just created a math mystery! You can draw a bar model and use your strategies to solve it. Keep practicing, and you'll be a math whiz!
Sample questions
Skills in this topic
- Fluently add numbers within 20 using various strategies (including making 10).
- Fluently subtract numbers within 20 using various strategies (including making 10).
- Solve for the unknown in addition and subtraction equations within 20.
- Apply addition and subtraction strategies to solve one-step word problems within 20 (using bar models).
- Formulate original word problems that require addition or subtraction within 20, and solve them.
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