Videos and solutions to help Kindergarten and Grade 1 kids learn to add and subtract within 20, demonstrating fluency for addition and subtraction within 10 by using decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9).

Common Core: 1.OA.6

### Learning Targets:

Related Topics:

Make Ten Addition, More Lessons for Grade 1, Common Core for Grade 1

Mental Math Strategies: Break Down to 10

In this video, Mr. Almeida explains how to use mental strategies to subtract within 20 using the "break down to 10" strategy. This is one of the strategies suggested in the Common Core State Standards for Mathematics, 1.OA.6 and 2.OA.2. With practice, this strategy can help students gain fluency when subtracting within 20. Eventually students will memorize these facts, which is expected by the end of grade 2.

14 - 9 = 14 - 4 - 5 = 10 - 5 = 5

15 - 7 = 15 - 5 - 2 = 10 - 2 = 8

17 - 8 = 17 - 7 - 1 = 10 - 1 = 9
Subtraction with the make a ten strategy

12 - 9 = 12 - 2 - 7 = 10 - 7 = 3

Make 10 Subtraction Strategy

11 - 6 = 11 - 1 - 5 = 10 - 5 = 5

13 - 9 = 13 - 3 - 6 = 10 - 6 = 4

17 - 8 = 17 - 7 - 1 = 10 - 1 = 9

14 - 7 = 14 - 4 - 3 = 10 - 3 = 7
Using Ten: a Mental Math Subtraction Strategy

Using Ten is a mental math strategy that involves changing a number to ten and then adjusting the answer. Because "10" is generally an easier number to work with, this simplifies the equation making it easier to solve.

13 - 8 = 10 - 8 + 3 = 5

You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

Common Core: 1.OA.6

- I can add and subtract within 10 easily.
- I can add and subtract by making 10. (e.g. 7 + 3 = 10, 10 - 6 = 4)

Related Topics:

Make Ten Addition, More Lessons for Grade 1, Common Core for Grade 1

Mental Math Strategies: Break Down to 10

In this video, Mr. Almeida explains how to use mental strategies to subtract within 20 using the "break down to 10" strategy. This is one of the strategies suggested in the Common Core State Standards for Mathematics, 1.OA.6 and 2.OA.2. With practice, this strategy can help students gain fluency when subtracting within 20. Eventually students will memorize these facts, which is expected by the end of grade 2.

14 - 9 = 14 - 4 - 5 = 10 - 5 = 5

15 - 7 = 15 - 5 - 2 = 10 - 2 = 8

17 - 8 = 17 - 7 - 1 = 10 - 1 = 9

12 - 9 = 12 - 2 - 7 = 10 - 7 = 3

11 - 6 = 11 - 1 - 5 = 10 - 5 = 5

13 - 9 = 13 - 3 - 6 = 10 - 6 = 4

17 - 8 = 17 - 7 - 1 = 10 - 1 = 9

14 - 7 = 14 - 4 - 3 = 10 - 3 = 7

Using Ten is a mental math strategy that involves changing a number to ten and then adjusting the answer. Because "10" is generally an easier number to work with, this simplifies the equation making it easier to solve.

13 - 8 = 10 - 8 + 3 = 5

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You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

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