Decimals

Multiplying and Dividing Decimals

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In Adding and Subtracting Decimals, you learned how to **add** decimal numbers. You may be able to think of times when you'd add decimals in real life. For example, let's say you go to the store and find a shirt you really like. The price tag says it costs $15.60. You like the shirt so much that you decide to buy five of them.

To figure out the total cost, you could **add** the prices.

Adding this many numbers could take a long time. In the lesson on multiplication, we learned that when you multiply, you are **increasing** a number many times. Because all of the shirt prices are the **same**, multiplication could help you solve this problem a little faster.

When you multiply decimal numbers, it's helpful to set up the problem in a way that makes it easier for you to solve it** one step at a time**.

Click through the slideshow below to learn how to set up a multiplication problem with decimals.

Multiplying decimal numbers is a lot like multiplying larger numbers. If you divide the large problem into a few smaller ones, it will be easier to solve. Let's see how this works by solving this problem: 2.3 x 4.

Click through the slideshow to learn how to multiply decimals.

**Note**: When determining where to place your decimal point in your answer, count the total number of digits to the right of **each** decimal point in your problem. For example, if you are simplifying 3.25 x 2.3, you would count the two digits in 3.25 plus the one digit in 2.3. Therefore, we should place the decimal point in our answer so that **three** digits are to the right (3.25 x 2.3 = 7.475).

Try solving these multiplication problems. Then, check your answer by typing it in the box.

7.15 x 5 =

2.67 x 3 =

6.66 x 4 =

Let's look at a different situation. Let's imagine you have a fence, and you want to plant 5 bushes in front of it. Your fence is 20 feet long. You'd like to space the bushes out equally, so you know you'll need to divide your fence into 5 equal sections. This means you'll need to divide 20 by 5.

In the lesson on division, we learned how to set up division expressions. For the situation above, the expression would look like this:

In our expression, 20 is a **whole number**. But what if the length of the fence is a **decimal number**? For instance, let's say it's 20.75 feet long. Believe it or not, dividing a decimal isn't that different.

When you set up an expression to divide a decimal number, it's important to make sure you're **always** dividing by a **whole number**. In our example above, 20.75 is being divided by the whole number 5. Dividing by a whole number makes long division easier to manage.

Click through the slideshow below to learn how to set up division problems with decimals.

In the previous slideshow, you practiced setting up division expressions with decimal numbers. Let's take a closer look at how to divide a decimal. Dividing a **decimal number** is a lot like dividing a **whole number**. There's just one extra step at the end.

Click through the slideshow to learn how to divide decimals.

Find the quotient for each of the long division problems below. Check your answer by typing it in the box.

4.62 ÷ 2 =

9.12 ÷ 3 =

4.41 ÷ 4.2 =

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