Lesson 1.3 · Estimating area (1)
Hua's Classroom for Shanghai Maths — One Lesson One Exercise (English edition, pages 7–9).
Lesson Alignment
How this Shanghai Maths lesson connects to learning goals, Common Core, and Eureka Math.
Learning Objectives
Students will be able to:
- 01Estimate the area of rectangles by rounding side lengths. (Question 1)
- 02Compare an estimate with an exact count on a grid. (Question 2)
- 03Explain when an estimate is reasonable. (Question 3)
- 04Apply estimation to real objects (books, desks). (Question 4–5)
Common Core Standards
| Code | Standard (focus for this lesson) |
|---|---|
| 3.MD.C.5 | Area as unit squares. |
| 3.MD.C.7 | Relate area to multiplication (length × width). |
| 3.NBT.A.1 | Use place value to round to nearest 10 or 100. |
Eureka Math Correspondence
| Shanghai Maths | Focus | Eureka Math |
|---|---|---|
| Q1–2 | Round then multiply | G3 M4 |
| Q3 | Reasonableness | G3 M2 estimation |
| Applications | Everyday objects | G3 M4 application |
Core Concepts
Round side lengths to friendly numbers, then multiply to estimate area.
Estimate Method
- Round each side to the nearest ten (or hundred).
- Multiply rounded length × rounded width.
- Label with square units (cm², m², …).
Example: $23\ ext{cm} imes 18\ ext{cm}$ → estimate $20 imes 20 = 400\ ext{cm}^2$.
Check on a Grid
Count unit squares for an exact area; compare with the estimate — they should be close if rounding was sensible.
Reasonableness
An estimate is reasonable if it is near the exact value and uses the correct units.
Key Terms & Definitions (Reference)
Quick glossary for this lesson.
| Term | Definition |
|---|---|
| Estimate | A close value found by rounding. |
| Exact area | Precise count or length × width. |
| Square unit | Unit for area (cm², m², …). |
Key Answers
Quick reference for this lesson’s exercise answers.
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