Download the Lessonotes Mobile Liberia app for faster lesson access on Android and iPhone.
Subject: Mathematics
Semester: 2
Period: 4
Week: 20
School Name:
Teacher’s Name:
Subject: Mathematics
Grade Level: Grade 4
Date: Week 20
Lesson Duration: 45 minutes
Week & Period: Week 20, Period 4
Topic: Estimating products & Multiplying 2-, 3-, 4-digit numbers by 2-digit numbers
Sub-topic: Vertical algorithm & estimation
Learning Objectives
By the end of the lesson, students should be able to:
- Estimate products to check reasonableness of answers.
- Multiply 2-, 3-, and 4-digit numbers by 2-digit numbers using vertical algorithm.
- Solve real-life word problems involving multiplication of large numbers.
Previous Knowledge
Students already know multiplication of 1-digit and multiples of 10, 100, and 1000.
Instructional Materials
Mathematics textbook for Grade 4, graph paper, number charts, calculators (optional).
Lesson Development – ABC Model
A – Anticipation (Warm-up / Starter)
Time: 5–10 minutes
Teacher presents: “Estimate 47 × 38” using rounded numbers: 50 × 40 = 2000. Students discuss why estimation is helpful.
B – Building Knowledge (Main Lesson Body)
Time: 25–30 minutes
Teacher introduces multiplication of two-digit and three-digit numbers using the distributive property and grid or column method, emphasizing breaking down one factor into parts and multiplying step-by-step. Also, introduce estimation as a powerful tool for verifying answers.
Step-by-step example: Multiply 235 × 42
Step 1: Break down 42 into 40 and 2
Step 2: Multiply 235 × 2 = 470
Step 3: Multiply 235 × 40 = 9,400
Step 4: Add the partial products: 470 + 9,400 = 9,870
Teacher models the process on the board, demonstrating clear alignment and addition of partial products, emphasizing place value understanding.
Additional Examples:
Example 2: Multiply 1,245 × 36
Break down 36 into 30 + 6
1,245 × 6 = 7,470
1,245 × 30 = 37,350
Sum: 7,470 + 37,350 = 44,820
Example 3: Multiply 3,652 × 27
Break down 27 into 20 + 7
3,652 × 7 = 25,564
3,652 × 20 = 73,040
Sum: 25,564 + 73,040 = 98,604
Estimation Practice:
Before calculating exactly, estimate the answer by rounding numbers to the nearest easy figure to multiply mentally.
Example: 1,245 × 36 ≈ 1,250 × 40 = 50,000 (Estimation to check reasonableness)
Learners’ Activities (Expanded):
- Students work in pairs to solve multiplication problems from real-life contexts, such as:
- Number of tickets sold (e.g., 324 tickets × 28 Naira per ticket)
- School supplies ordered (e.g., 145 desks × 36 classrooms)
- They use grid or column methods, clearly showing partial products and sums.
- Each pair estimates their answer first, then performs exact multiplication, comparing the two results to check for reasonableness.
- Peer discussion on when estimation might overestimate or underestimate the actual product.
Assessment Checks:
- Estimate first, then calculate: 324 × 28.
(Expected: Estimate: 320 × 30 = 9,600; Actual calculation: 324 × 28 = 9,072) - Explain how estimation helps verify results in multiplication.
- Multiply 457 × 23 using the grid or column method.
- Estimate and calculate: 1,112 × 19.
- Why is it important to align digits correctly in the vertical multiplication method?
Notes (Expanded & Detailed):
• Estimation simplifies complex multiplication by rounding numbers to nearest tens or hundreds, allowing quick mental checks that help ensure answers are reasonable and reduce careless errors.
• The vertical algorithm or grid method breaks down multiplication into manageable partial products, helping maintain place value accuracy.
• Practicing multiplication with larger numbers enhances calculation speed and accuracy, which is critical in higher-level math and real-life applications like budgeting, inventory, or data analysis.
• Estimation also builds number sense, helping learners understand the scale of numbers and the expected size of results.
• Teachers should reinforce the importance of writing digits in the correct place to avoid errors in carrying and addition.
C – Consolidation (Conclusion & Assessment)
Time: 5–10 minutes
Summary: Estimation and vertical algorithm together make multiplication of large numbers manageable and accurate.
Evaluation Method (Expanded):
Exit slip: Multiply 456 × 34 and estimate first.
Teacher provides oral feedback.
Assignment (Expanded):
Multiply 245 × 36, 1,123 × 27.
Create a word problem using any of the products.
Follow-up Activity:
Peer review of multiplication problems using graph paper and arrays.
Differentiation / Inclusive Strategies
Step-by-step guidance for struggling learners; challenge advanced learners with larger numbers or multi-step word problems.
Teacher’s Reflection (After Class)
What worked well? ___________________________________________
What needs improvement? ____________________________________
Students’ engagement level: ☑ High ☑ Medium ☑ Low