Calculate Parallelogram Area: Rectangle with Perimeter 24 Inside

Question

The parallelogram ABCD contains the rectangle AEFC inside it, which has a perimeter of 24.

AE = 8

BC = 5

P=24P=24P=24555AAABBBCCCDDDEEEFFF8

What is the area of the parallelogram?

Video Solution

Solution Steps

00:17 Let's find the area of the parallelogram!
00:20 Remember, opposite sides are equal in a rectangle.
00:27 The perimeter is the total length of all sides added together.
00:36 Let's plug in the numbers and solve for E C.
00:55 We've found the length of E C. It's also the height of the parallelogram.
01:01 Now, we'll use the Pythagorean theorem in triangle E B C.
01:11 Let's substitute the numbers and find E B.
01:17 Next, we need to isolate E B.
01:24 Great! We now know the length of E B.
01:34 Let's calculate the area by multiplying the height by the base.
01:41 The side A B equals the sum of A E and E B.
01:45 Now we'll use the values to find the area of the parallelogram.
01:50 And there we have it! We've solved the problem.

Step-by-Step Solution

In the first step, we must find the length of EC, which we will identify with an X.

We know that the perimeter of a rectangle is the sum of all its sides (AE+EC+CF+FA),

Since in a rectangle the opposite sides are equal, the formula can also be written like this: 2AE=2EC.

We replace the known data:

2×8+2X=24 2\times8+2X=24

16+2X=24 16+2X=24

We isolate X:

2X=8 2X=8

and divide by 2:

X=4 X=4

Now we can use the Pythagorean theorem to find EB.

(Pythagoras: A2+B2=C2 A^2+B^2=C^2 )

EB2+42=52 EB^2+4^2=5^2

EB2+16=25 EB^2+16=25

We isolate the variable

EB2=9 EB^2=9

We take the square root of the equation.

EB=3 EB=3

The area of a parallelogram is the height multiplied by the side to which the height descends, that isAB×EC AB\times EC .

AB= AE+EB AB=\text{ AE}+EB

AB=8+3=11 AB=8+3=11

And therefore we will apply the area formula:

11×4=44 11\times4=44

Answer

44