CCSS.Math.Content.2.MD.B.5
The standard
Use addition and subtraction within 100 to solve word problems involving lengths that are given in the same units, e.g., by using drawings (such as drawings of rulers) and equations with a symbol for the unknown number to represent the problem.
Common Core State Standards for Mathematics · Measurement and Data
What this standard means
Students need to solve length word problems using addition and subtraction within 100. The lengths use the same unit, like inches, feet, centimeters, or meters. They should show their thinking with a drawing, a ruler sketch, a number line, or an equation with a missing number.
Mastery looks like choosing the right operation, labeling the unit, and explaining what the unknown number means. Students often get stuck when the problem compares two lengths, or when the unknown is not at the end, like 35 + __ = 62.
Ways to teach it
- Give pairs paper strips with centimeter lengths, then ask them to find total length and length difference using drawings and equations.
- Ask, “Mia’s ribbon is 48 cm and Leo’s is 19 cm shorter. How long is Leo’s ribbon?” Explain with a sketch.
- Show three problems and have students circle add or subtract, write an equation, and solve one within five minutes.
- Measure two classroom objects in inches, then write and solve a word problem about their total length or difference.
Plan a lesson for CCSS.Math.Content.2.MD.B.5
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Related standards
- CCSS.Math.Content.1.OA.A.1
Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, wit...
- CCSS.Math.Content.3.OA.A.3
Use multiplication and division within 100 to solve word problems in situations involving equal groups, arrays, and measurement quantities, e.g., by using drawi...
- CCSS.Math.Content.2.OA.A.1
Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart,...
- CCSS.Math.Content.K.OA.A.2
Solve addition and subtraction word problems, and add and subtract within 10, e.g., by using objects or drawings to represent the problem.