Unit Plan 8 (Grade 3 Math): Time & Intervals—Word Problems with All Operations
Build fluency telling and writing time to the minute, finding elapsed time with timelines, and solving one- and two-step word problems using equations with unknowns—checking reasonableness with benchmarks and inverse thinking.
Focus: Tell/write time to the minute, compute elapsed time, and solve one- and two-step problems using timelines/number lines and equations.
Grade Level: 3
Subject Area: Mathematics (Measurement & Data; Operations)
Total Unit Duration: 5 sessions (one week), 45–60 minutes per session
I. Introduction
Students build fluency reading analog and digital clocks to the minute, then use elapsed time strategies—especially timeline/number line models—to find start, end, or duration. They apply these skills to one- and two-step word problems, write equations with an unknown, and check reasonableness.
Essential Questions
- How do timeline/number line models help me make sense of elapsed time?
- When do I add time and when do I subtract time?
- How can I represent and check a two-step time problem for reasonableness?
II. Objectives and Standards
Learning Objectives — Students will be able to:
- Tell and write time to the minute on analog/digital clocks and use a.m./p.m. correctly.
- Compute elapsed time across hour boundaries using timeline (add-up/count-back) strategies and 60 minutes = 1 hour conversions.
- Solve one- and two-step word problems that include time plus another operation (e.g., add minutes, then subtract), representing with equations and a letter for the unknown.
- Evaluate reasonableness using estimation, benchmarks (quarter/half hour), and inverse checks.
- Explain and critique solutions using clear units, labels, and models.
Standards Alignment — CCSS Grade 3
- 3.MD.1: Tell and write time to the nearest minute; measure time intervals in minutes; solve word problems involving addition and subtraction of time intervals in minutes, and represent on a number line diagram.
- 3.OA.8: Solve two-step word problems using the four operations; represent with equations using a letter for the unknown; assess reasonableness using mental computation and estimation (including rounding).
- Mathematical Practices: MP.4 (Model with mathematics) emphasized.
Success Criteria — Student Language
- I can read time to the minute and label a.m./p.m.
- I can find elapsed time with a timeline/number line and convert minutes ↔ hours.
- I can write an equation with a letter for the unknown and check my answer for reasonableness.