CCSS.Math.Content.7.EE.A.2
The standard
Understand that rewriting an expression in different forms in a problem context can shed light on the problem and how the quantities in it are related.
Common Core State Standards for Mathematics · Expressions and Equations
What this standard means
Students need to see that two expressions can look different but mean the same thing. They should connect the form of an expression to the situation, not just simplify by habit. For example, x + 0.20x shows the original amount plus 20%, while 1.20x shows the new total after the increase.
Mastery looks like choosing or rewriting an expression to make a relationship clearer, then explaining why the forms match. Students often get stuck treating symbols as steps to follow instead of quantities with meaning. Percent increase, tax, discounts, combining like terms, and distributive form are common trouble spots.
Ways to teach it
- Give pairs algebra tiles or paper strips to model 3x + 2x, then rewrite it as 5x and explain what stayed the same.
- Ask students: Which form is clearer for a 15% tip, p + 0.15p or 1.15p, and why?
- Show 4(n + 3) and 4n + 12, then ask students to write one sentence proving they are equivalent.
- Use a store receipt with sales tax and have students write two equivalent expressions for the final cost.
Plan a lesson for CCSS.Math.Content.7.EE.A.2
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Related standards
- CCSS.Math.Content.HSA-SSE.A.2
Use the structure of an expression to identify ways to rewrite it.
- CCSS.Math.Content.HSA-SSE.B.3
Choose and produce an equivalent form of an expression to reveal and explain properties of the quantity represented by the expression.
- CCSS.Math.Content.HSA-SSE.B
Write expressions in equivalent forms to solve problems
- CCSS.Math.Content.HSF-IF.C.8
Write a function defined by an expression in different but equivalent forms to reveal and explain different properties of the function.