Unit Plan 17 (Grade 3 Math): Measurement—Mass & Volume Word Problems
Solve real-world mass (g/kg) and volume (L) word problems—one- and two-step—by modeling situations, writing equations with unknowns, and checking reasonableness using consistent units.
Focus: Use grams/kilograms and liters to solve one- and two-step word problems with all four operations; model situations, write equations with an unknown, and check reasonableness with units.
Grade Level: 3
Subject Area: Mathematics (Measurement & Data • Operations connection)
Total Unit Duration: 5 sessions (one week), 45–60 minutes per session
I. Introduction
Students build concrete understanding of mass and volume and apply operations in contextual problems. They estimate, measure, and record units (g, kg, L), write equations with unknowns, and explain why their solutions are reasonable for the context (e.g., juice batches, snack packs, science materials).
Essential Questions
- How do mass and volume show up in real-life problems?
- How do I choose the operation(s) and keep units consistent?
- How do models and equations help me solve and justify multi-step problems?
II. Objectives and Standards
Learning Objectives — Students will be able to:
- Distinguish mass (grams/kilograms) from volume (liters) and select appropriate tools to measure.
- Solve one-step mass/volume problems using addition or subtraction with correct units.
- Solve two-step problems (mixed operations) by modeling, writing an equation with an unknown, and justifying steps.
- Use estimation to plan and to check the reasonableness of answers.
- Communicate solutions with units, labels, and clear representations.
Standards Alignment — CCSS Grade 3
- 3.MD.2: Measure and estimate liquid volume and mass using liters (L), grams (g), kilograms (kg); solve one-step word problems in the same units using the four operations.
- 3.OA.8: Solve two-step word problems using the four operations; represent with equations and a letter for the unknown; assess reasonableness.
- Mathematical Practices: MP.4 (Model with mathematics) threaded; MP.2 (Reason quantitatively), MP.6 (Precision).
Success Criteria — Student Language
- I can tell whether a problem is about mass (g/kg) or volume (L).
- I can choose the operation(s), write an equation with an unknown, and solve with correct units.
- I can estimate first and check if my answer is reasonable for the situation.