Chapter 2 · Multiplying by a one-digit number
Lesson 2.5 · Multiplying a two-digit number by a one-digit number (2)
Hua's Classroom for Shanghai Maths — One Lesson One Exercise (English edition, pages 25–26).
Lesson Alignment
How this Shanghai Maths lesson connects to learning goals, Common Core, and Eureka Math.
Learning Objectives
Students will be able to:
- 01Multiply two-digit × one-digit with the column method. (Basic)
- 02Check using split, estimate, or inverse operations.
- 03Find and correct errors in vertical calculations.
- 04Solve money / quantity word problems.
Common Core Standards
| Code | Standard (focus for this lesson) |
|---|---|
| 3.OA.A.3 | Word problems. |
| 3.NBT.A.3 | Place-value strategies / algorithms. |
| 3.OA.B.5 | Properties as strategies. |
Eureka Math Correspondence
| Shanghai Maths | Focus | Eureka Math |
|---|---|---|
| Standard algorithm | Two-digit × one-digit | G3 M3 |
| Error analysis | Regrouping | G3 M3 fluency |
Core Concepts
Use the column method for two-digit × one-digit and check with another method.
Column Method
- Multiply ones by the one-digit factor; regroup if needed.
- Multiply tens; add any regrouped tens.
- Write the product.
Example story: cost of 3 model boats — multiply unit price × 3.
Check the Answer
- Split method: tens product + ones product.
- Estimate: $19 \times 4 \approx 20 \times 4 = 80$.
- Inverse: divide the product by the one-digit factor.
Find & Fix Errors
Textbook asks students to correct mistakes in a box — good interview talk: “Where did the regrouping go wrong?”
Key Terms & Definitions (Reference)
Quick glossary for this lesson.
| Term | Definition |
|---|---|
| Column method | Vertical algorithm lined up by place value. |
| Regroup | Carry tens when a place is 10 or more. |
| Estimate | Nearby easy product to check. |
Key Answers
Quick reference for this lesson’s exercise answers.
Key answers
- $3×81=243$ yuan
- $49×4=196$ (check: $4×40=160$, $4×9=36$, $160+36=196$)
- Column method: $4×62=248$; $32×2=64$; $4×18=72$; $43×6=258$; $7×51=357$
- Corrections: $14×4=56$; $53×3=159$
- Multiple choice: (1) D (2) least divisor D ($7$); dividend A ($139$)
- $□□×8=272 ⇒ 34×8=272$
- $13-10=3$