CCSS.Math.Content.7.NS.A.1
The standard
Apply and extend previous understandings of addition and subtraction to add and subtract rational numbers; represent addition and subtraction on a horizontal or vertical number line diagram.
Common Core State Standards for Mathematics · The Number System
What this standard means
Students need to add and subtract positive and negative rational numbers, including fractions and decimals, and show the moves on a number line. They should connect “add” with moving in the direction of the sign and connect subtraction with adding the opposite.
Mastery looks like choosing a good number line scale, placing values accurately, and explaining why an answer is positive, negative, or zero. Students often get stuck when subtracting negatives, mixing fraction and decimal forms, or treating the number line as just a picture instead of a tool for reasoning.
Ways to teach it
- Have students use masking tape number lines and fraction cards to physically walk sums like -1/2 + 3/4 and -2 - 1.5.
- Ask students to explain in writing why 4 - (-3) gives the same result as 4 + 3 using a number line.
- Give four problems, two addition and two subtraction, and ask students to solve one with a number line and one with symbols.
- Use temperature changes from a weather report to model adding and subtracting rational numbers, such as a drop of 6.5 degrees from -2 degrees.
Plan a lesson for CCSS.Math.Content.7.NS.A.1
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Related standards
- CCSS.Math.Content.6.NS.C.6
Understand a rational number as a point on the number line. Extend number line diagrams and coordinate axes familiar from previous grades to represent points on...
- CCSS.Math.Content.7.NS.A.2
Apply and extend previous understandings of multiplication and division and of fractions to multiply and divide rational numbers.
- CCSS.Math.Content.6.NS.C
Apply and extend previous understandings of numbers to the system of rational numbers.
- CCSS.Math.Content.7.NS.A
Apply and extend previous understandings of operations with fractions to add, subtract, multiply, and divide rational numbers.