Maryland Math 7.NOS.A.1.b
The Standard
- 7.NOS.A.1
- Add and subtract rational numbers using multiple strategies and representations.
Model the addition of rational numbers as movement along a number line, where the direction and distance depend on the sign and magnitude of the addend. Show that a number and its opposite have a sum of 0 (are additive inverses).
Maryland College and Career Ready Standards for Mathematics (2025) · USE STRUCTURE AND REPRESENTATIONS TO REASON WITH RATIONAL NUMBERS.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Start at the first number on a number line. Move right for a positive addend or left for a negative addend, by the addend’s distance from zero. Show that adding a number and its opposite brings them back to zero.
What Mastery Looks Like
- For -1.5 + 2.25, a student starts at -1.5, moves 2.25 units right, and lands at 0.75. They can draw arrows for 3/4 + (-3/4) and explain why the endpoint is zero.
Common Misconceptions
- Students may move left because the starting number is negative, even when the addend is positive. They may use the sign as the distance to move. Some think a number and its opposite cannot add to zero because one is negative.
How to Assess It
- On an exit ticket, ask students to draw and label the moves for -2.5 + 1.5 and 2.5 + (-2.5). Have them write each endpoint and explain why one sum is zero.
Lesson moves
Ways to Teach It
Tape a number line in half-unit increments; students walk 2.5 units right, then 2.5 left, and name the endpoint.
Ask: Why does -1/2 + 3/4 move right, even though the first number is negative? Draw arrows to support your answer.
Give pairs signed fraction cards; students draw two, sketch the moves, and score a point when opposite cards return them to zero.
On a horizontal temperature number line, mark -3°C and draw a 5°C warming to show the new temperature.
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Related Standards
- 7.NOS.A.1.c
Rewrite subtraction as addition using the additive inverse (p − q = p + (−q)). Use strategies such as number lines and applying absolute value of the difference...
- 7.NOS.A.2.a
Model multiplication of rational numbers using number lines, arrays, or area models to show how properties of operations (e.g., the distributive property) lead ...
- 6.NOS.C.6.c
Recognize and locate opposite signs of rational numbers as indicating locations on opposite sides of 0 on the number line.
- 7.NOS.A.1
Add and subtract rational numbers using multiple strategies and representations.
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