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**

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.

Examples:

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**

Example:

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

**Make 10 Subtraction Strategy**

Examples:

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.

Example:

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

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.

Examples:

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

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

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

Example:

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

Examples:

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.

Example:

13 - 8 = 10 - 8 + 3 = 5

Rotate to landscape screen format on a mobile phone or small tablet to use the **Mathway** widget, a free math problem solver that **answers your questions with step-by-step explanations**.

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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