# 4.7: Distributive Property to Evaluate Formulas with Decimals

**At Grade**Created by: CK-12

**Practice**Distributive Property to Evaluate Formulas with Decimals

Have you ever had to use a formula to figure something out? Well sometimes when you work with properties, it is necessary.

Let's say that you had a rectangle that was half as large as this one. That would mean that the side lengths of the rectangle would be 6 inches and 3.5 inches.

Now what if you had two of them? What would be the area of the two rectangles?

2(6 x 3.5)

Do you know how to figure this out?

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This Concept is about the distributive property and formulas. By the end of it, you will know how to tackle this problem.
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### Guidance

We can also use and apply the Distributive Property when working with a formula. Let’s think about the formula for finding the area of a rectangle.

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We know that the area of a rectangle can be found by using the formula:
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For this example, we would multiply 12 times 4 and get an area of 48 square inches.

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How can we find the area of both of these rectangles?
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You can see that they have the same width. The width is four and a half inches. However, there are two lengths.

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We need to find the product of a number and a sum.
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Here is our expression.
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Now we can use the Distributive Property to find the area of these two rectangles.

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Notice that we used what we have already learned about multiplying decimals and whole numbers with the Distributive Property.
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When we distributed 4.5 with each length, we were able to find the sum of the products.
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This gives us the area of the two rectangles.
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Use what you have learned to answer these questions about formulas, area and the distributive property.

#### Example A

What is the formula for finding the area of a square?

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Solution: A = s^2
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#### Example B

Which property is being illustrated: 4(a + b) = 4a + 4b

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Solution: The Distributive Property
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#### Example C

What is the formula for finding the area of a rectangle?

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Solution: A = length x width
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Remember the rectangle from the beginning of the Concept? Now you are ready to work on that problem. Take a look.

Let's say that you had a rectangle that was half as large as this one. That would mean that the side lengths of the rectangle would be 6 inches and 3.5 inches.

Now what if you had two of them? What would be the area of the two rectangles?

2(6 x 3.5)

Do you know how to figure this out?

To figure this out, we have to multiply the value outside the parentheses by both values inside the parentheses.

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The area of the two rectangles is 84 square inches.
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### Guided Practice

Here is one for you to try on your own.

Use the Distributive Property to find the area of the rectangles.

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Answer
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First, we can write an expression to solve it.

Next, we can solve it.

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The area of the two rectangles is
.
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### Video Review

Khan Academy The Distributive Property

Khan Academy: Area and Perimeter

### Explore More

Directions: Practice using the Distributive Property to solve each problem.

1. 3.2(4 + 7)

2. 2.5(6 + 8)

3. 1.5(2 + 3)

4. 3.1(4 + 15)

5. 6.5(2 + 9)

6. 7.5(2 + 3)

7. 8.2(9 + 3)

8. 4(5.5 + 9)

9. 5(3.5 + 7)

10. 2(4.5 + 5)

11. 3.5(2.5 + 3)

12. 2.5(9 + 1.5)

13. 3.2(7 + 8.3)

14. 1.5(8.9 + 2.5)

15. 3.5(2.5 + 8.2)

### Image Attributions

## Description

## Learning Objectives

Here you'll learn to use the Distributive Property to evaluate formulas using decimal quantities.