Multiplying Decimals Using the Standard Algorithm

This lesson teaches how to multiply decimals using the standard algorithm. It begins with a review of multiplication concepts using array models and base 10 blocks. The lesson then explains the differences between multiplying whole numbers and decimals, emphasizing that decimal products are smaller than the factors. Detailed steps for multiplying decimals are provided, including estimating the product, stacking numbers, and placing the decimal point. Examples illustrate these steps, and the lesson concludes with a summary of the key points.

What is the purpose of using an array model in multiplication?

• To subtract numbers efficiently

• To add numbers quickly

• To visualize multiplication

• To divide numbers easily

When multiplying whole numbers, what is true about the products?

• They are always decimals

• They are always whole numbers

• They are always larger than the factors

• They are always smaller than the factors

What is the first step in multiplying decimals using the standard algorithm?

• Stack the numbers vertically

• Convert to whole numbers

• Estimate the product

• Insert the decimal point

How do you determine where to place the decimal point in the product?

• By subtracting the smaller factor from the larger one

• By dividing the product by 10

• By adding the factors together

• By counting the total number of decimal places in the factors

In the example of 4.08 times 0.8, how many places do you move the decimal point in the product?

• Two places to the left

• One place to the right

• Three places to the left

• One place to the left

Why do we convert decimals to whole numbers before multiplying?

• To avoid using decimals

• To decrease the product

• To increase the product

• To make the multiplication process easier

After converting decimals to whole numbers and multiplying, what must be done to the product?

• Multiply the product by 10

• Move the decimal point back to its original position

• Subtract 100 from the product

• Add 10 to the product