Using mental strategies to add and subtract within 20 is a second grade, Common Core math skill: 2.OA.2. Below we show two videos that demonstrate each of these standards. Then, we provide a breakdown of the specific steps in the videos to help you teach your class.
Your students should be experienced in solving all types of addition and subtraction problems. Before, “addition” was separate from subtraction, and the problems were limited to one-step problems and numbers within 20 (1.OA.1).
After learning these math skills, your students will be able to apply strategies to both one and two-step problems that involve the “four operations (addition, subtraction, multiplication, division).” Additionally, your students will learn how to represent an unknown using a letter (3.OA.8).
Common Core Standard: 2.OA.2 - Fluently add and subtract within 20 using mental strategies
Students who understand this principle can:
2 Videos to Help You Teach Common Core Standard: 2.OA.2
Below we provide and breakdown two videos to help you teach your students this standard.
Video 1: Adding and Subtracting while Exercising
The video opens on a young woman in the middle of her workout routine. Her online instructor, Anaya, told her to do 15 squats, she’s already done 7. Because she knows her math facts, she knows how many more squats she needs to do.
The speaker explains why knowing how to mentally solve math problems quickly is important. Then she moves onto the next exercise—crunches.
At the end of the video, the speaker tells students that they will learn to meantally add and subtract within 20 in this quest or lesson.
Video 2: Practice Adding and Subtracting with Boddle
The video starts by introducing the topic: adding and subtracting within 20. Boddle starts with the basics by asking students to solve simple addition and subtraction problems.
Next, Boddle flips it around and has students match the answer to the correct math equation. Doing so helps students learn to approach problems from multiple angles.
Which addition or subtraction problem makes the number on the left?
Afterwards, Boddle has students find the missing number in a set of equations.
Boddle congratulates students on their excellent work and drives away till next time.
Want more practice?
Give your students additional standards-aligned practice with Boddle Learning. Boddle includes questions related to Comparing and Measuring Lengths plus rewarding coins and games for your students to keep them engaged. Click here to sign up for Boddle Learning and create your first assignment today.
*Information on standards is gathered from The New Mexico Public Education Department's New Mexico Instructional Scope for Mathematics and the Common Core website.