Lesson: Multiplying Decimals

In this lesson, we will learn how to multiply decimals effectively.

Steps for Multiplying Decimals

1. Ignore the Decimal Points: Treat the decimals as whole numbers.
2. Multiply the Numbers: Perform the multiplication as if there are no decimals.
3. Count the Decimal Places: Count how many total decimal places are in the numbers you multiplied.
4. Place the Decimal Point: In the product, place the decimal point so that it has the same number of decimal places as the total counted in step 3.

Example

Let's multiply $2.5$ and $3.4$:

1. Ignore the decimals: $25$ and $34$.
2. Multiply the numbers: $$25 \times 34 = 850$$
3. Count the decimal places: $2$ (one in $2.5$ and one in $3.4$).
4. Place the decimal: Since we counted $2$ decimal places, we write it as $8.50$ or simply $8.5$.

So, $2.5 \times 3.4 = 8.5$.

Key Questions

• What do you do first when multiplying decimals?
• How do you determine where to place the decimal in the final product?
• Can you provide another example of multiplying decimals?

Review

Multiplying decimals involves treating them as whole numbers, performing the multiplication, and then correctly placing the decimal based on the total decimal places in the original numbers.