Multiplying large numbers

Lesson: Multiplying Large Numbers

Lesson Objectives:

Understand multiplication as repeated addition.

Learn to multiply numbers with more than two digits.

Use the vertical multiplication (long multiplication) method to solve problems.

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1. What is Multiplication?

Multiplication is a way of doing repeated addition.

Example:

If we have 4 boxes, and each box has 6 apples:

> 6 + 6 + 6 + 6 = 24

This is the same as:

4 × 6 = 24

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2. Parts of a Multiplication Expression

In the equation:

3 × 5 = 15

The first number (3) is called a factor

The second number (5) is also a factor

The result (15) is called the product

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3. Vertical (Long) Multiplication

Example: Multiply 243 × 5

Write the numbers in column form:

243

× 5

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Start multiplying from the right:

5 × 3 = 15 → write 5, carry 1

5 × 4 = 20 + 1 = 21 → write 1, carry 2

5 × 2 = 10 + 2 = 12

Final Answer: 1215

More Examples:

Example 1:

Multiply: 312 × 4

Steps:

312

× 4

-------

4 × 2 = 8

4 × 1 = 4

4 × 3 = 12

Answer: 1248

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Example 2:

Multiply: 125 × 6

Steps:

125

× 6

-------

6 × 5 = 30 → write 0, carry 3

6 × 2 = 12 + 3 = 15 → write 5, carry 1

6 × 1 = 6 + 1 = 7

Answer: 750

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Practice Questions:

1. 341 × 3 = ______

2. 208 × 5 = ______

3. 129 × 4 = ______

4. 452 × 6 = ______

5. 601 × 7 = ______