Find X in Rectangle: Area 40 cm² with Side Length 2x+4

Rectangle ABCD has an area of

40 cm².

Side BC is equal to 5 cm.
Work out the value of x.
S=40S=40S=402x+42x+42x+4555AAABBBCCCDDD

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:13 Let's find the value of X.
00:16 First, we'll use the formula for the area of a rectangle.
00:20 Multiply side A-B by side B-C.
00:24 Now, plug in the numbers and solve for X.
00:29 Be sure to open the parentheses carefully.
00:35 Next, let's isolate X.
00:39 And there you go, that's how we find the solution!

Step-by-step written solution

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1

Understand the problem

Rectangle ABCD has an area of

40 cm².

Side BC is equal to 5 cm.
Work out the value of x.
S=40S=40S=402x+42x+42x+4555AAABBBCCCDDD

2

Step-by-step solution

Let's multiply side AB by side BC

We'll set up the data as follows:

5(2x+4)=40 5(2x+4)=40

Let's multiply 5 by each term in parentheses:

10x+20=40 10x+20=40

We'll move 20 to the right side and change its sign accordingly:

10x=4020 10x=40-20

Now we get:

10x=20 10x=20

Let's divide both sides by 10:

x=2 x=2

3

Final Answer

2

Practice Quiz

Test your knowledge with interactive questions

Look at the rectangle ABCD below.

Side AB is 6 cm long and side BC is 4 cm long.

What is the area of the rectangle?
666444AAABBBCCCDDD

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