Intermediate Geometry : How to find the area of a parallelogram

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #1 : How To Find The Area Of A Parallelogram

The perimeter of a square is \(\displaystyle 24\; in\).  If the sides of the square are reduced by a factor of two, what is the area of the new square?

Possible Answers:

\(\displaystyle 18\; in^{2}\)

\(\displaystyle 9\; in^{2}\)

\(\displaystyle 27\; in^{2}\)

\(\displaystyle 45\; in^{2}\)

\(\displaystyle 36\; in^{2}\)

Correct answer:

\(\displaystyle 9\; in^{2}\)

Explanation:

The perimeter of a square is geven by \(\displaystyle P=4s\) and the area of a square is given by \(\displaystyle A=s^{2}\)

Thus \(\displaystyle P=4s=24\: in\)

so \(\displaystyle s=6\; in\)

The original side is reduced by a factor of \(\displaystyle 2\) which results in a new side of \(\displaystyle 3\; in\).  The area of the new square is geven by

\(\displaystyle A=s^{2}=3^{2}=9\; in^{2}\)

Example Question #2 : How To Find The Area Of A Parallelogram

Find the area of the box in square inches: 

Geo_box

Possible Answers:

\(\displaystyle 84xy\)

\(\displaystyle 12x +7y\)

\(\displaystyle x + y + 19\)

\(\displaystyle 2x + 2y + 38\)

\(\displaystyle xy + 7x + 12y +84\)

Correct answer:

\(\displaystyle xy + 7x + 12y +84\)

Explanation:

The answer is \(\displaystyle xy + 7x + 12y +84\).  You can find the area of this box by multiplying the length by its width:

Foil  \(\displaystyle (12 + x) (7 + y ) = xy + 7x + 12y +84\)

 

 If you chose \(\displaystyle 2x + 2y + 38\), you added the sides to get the perimeter. 

 

Just remember, the width is 12 added to \(\displaystyle x\).  Not 12 times the side of \(\displaystyle x\)

Example Question #2 : How To Find The Area Of A Parallelogram

If all angles are right angles in the figure below, what is the total area of the figure? 

Box1

Possible Answers:

\(\displaystyle 256\ in^{2}\)

\(\displaystyle 308\ in^{2}\)

\(\displaystyle 152\ in^{2}\)

\(\displaystyle 164\ in^{2}\)

\(\displaystyle 184\ in^{2}\)

Correct answer:

\(\displaystyle 164\ in^{2}\)

Explanation:

The answer is \(\displaystyle 164\ in^{2}\)

To get the area, you would need to find the missing sides.  Since the horizontal top is \(\displaystyle 8+8=16\) inches total, the bottom must be \(\displaystyle 16\) inches total. Thus you would subtract \(\displaystyle 16-6\) to get \(\displaystyle 10\) for the missing bottom horizontal side. 

The vertical right side is \(\displaystyle 4+12 = 16\) inches total.  Then you would subtract \(\displaystyle 16-10\) to get \(\displaystyle 6\) for the missing vertical side.  

Then you would have to split the figure into 3 different boxes and find the area of each one.  Then you would add the area of each box

\(\displaystyle (32+60+72)=164\ in ^{2}\)

Example Question #1 : How To Find The Area Of A Parallelogram

What is the area of a parallelogram if the base is \(\displaystyle 1.5\:cm\), and the height is \(\displaystyle 1.0\:cm\)?

Possible Answers:

\(\displaystyle 0.25\:cm\)

\(\displaystyle 0.75\:cm\)

\(\displaystyle 3\:cm\)

\(\displaystyle 1.5\sqrt2\:cm\)

\(\displaystyle 1.5\:cm\)

Correct answer:

\(\displaystyle 1.5\:cm\)

Explanation:

The formula for the area of a parallelogram is:

\(\displaystyle A=base\cdot height\)

So, we are given all of the information that we need to solve this problem. Substitute the provided values into the equation and simplify:

\(\displaystyle A= (1.5\:cm)(1\:cm) =1.5\:cm^2\)

Example Question #5 : How To Find The Area Of A Parallelogram

What is the area of a parallelogram if the base is \(\displaystyle 2x\:cm\) and the height is \(\displaystyle x^2\:cm\)?

Possible Answers:

\(\displaystyle 2x^3\:cm^2\)

\(\displaystyle x^3\:cm^2\)

\(\displaystyle 2x+x^2\:cm^2\)

\(\displaystyle 2\sqrt2x^3\:cm^2\)

\(\displaystyle 2x^2\:cm^2\)

Correct answer:

\(\displaystyle 2x^3\:cm^2\)

Explanation:

The formula for the area of a parallelogram is:

\(\displaystyle A=base\cdot height\)

Substitute in the provided values and simplify to calculate the correct answer:

\(\displaystyle A= (2x\:cm)(x^2\:cm) =2x^3\:cm^2\)

Example Question #6 : How To Find The Area Of A Parallelogram

Find the area of a parallelogram if the base is \(\displaystyle (x-2)\) and the height is \(\displaystyle (x+4)\).

Possible Answers:

\(\displaystyle x^2+2x-8\)

\(\displaystyle 4x+4\)

\(\displaystyle 2x+2\)

\(\displaystyle x^2-2x-8\)

\(\displaystyle x^2-8\)

Correct answer:

\(\displaystyle x^2+2x-8\)

Explanation:

The formula for the area of a parallelogram is:

\(\displaystyle A=base\cdot height\)

Substitute the values provided in the question:

\(\displaystyle A= (x-2)(x+4)\)

Use the FOIL method to simplify:

\(\displaystyle A=(x)(x)+(x)(4) +(-2)(x)+(-2)(4)\)

\(\displaystyle A= x^2+4x-2x-8\)

\(\displaystyle A=x^2+2x-8\)

Example Question #3 : How To Find The Area Of A Parallelogram

What is the area of a parallelogram if the base is \(\displaystyle \sqrt2\:cm\) and the height is \(\displaystyle \sqrt3\:cm\)?

Possible Answers:

\(\displaystyle \frac{\sqrt6}{2}\:cm^2\)

\(\displaystyle \frac{\sqrt5}{2}\:cm^2\)

\(\displaystyle \sqrt2 + \sqrt3\:cm^2\)

\(\displaystyle \sqrt6\:cm^2\)

\(\displaystyle \sqrt5\:cm^2\)

Correct answer:

\(\displaystyle \sqrt6\:cm^2\)

Explanation:

The formula for the area of a parallelogram is:

\(\displaystyle A=base\cdot height\)

Substitute the values provided in the problem and solve to calculate the correct answer:

\(\displaystyle A= (\sqrt2\:cm)(\sqrt3\:cm) =\sqrt6\:cm^2\)

Example Question #1 : How To Find The Area Of A Parallelogram

If the height of the parallelogram is half of the length of the rectangle, then find the area of the shaded region in the figure.

2

Possible Answers:

\(\displaystyle 6\)

\(\displaystyle 9\)

\(\displaystyle 8\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 9\)

Explanation:

13

In order to find the area of the shaded region, we must first find the areas of the rectangle and parallelogram.

Recall how to find the area of a rectangle:

\(\displaystyle \text{Area of Rectangle}=\text{length}\times\text{width}\)

Substitute in the given length and height to find the area of the rectangle.

\(\displaystyle \text{Area of Rectangle}=2 \times 6\)

\(\displaystyle \text{Area of Rectangle}=12\)

Next, find the area of the parallelogram.

Recall how to find the area of a parallelogram:

\(\displaystyle \text{Area of Parallelogram}=\text{base}\times\text{height}\)

We need to find the height of the parallelogram. From the question, we know the following relationship:

\(\displaystyle \text{height}=\frac{\text{length}}{2}\)

Substitute in the length of the rectangle to find the height of the parallelogram.

\(\displaystyle \text{height}=\frac{2}{2}\)

\(\displaystyle \text{height}=1\)

Now, substitute in the height and the given length of the base to find the area of the parallelogram.

\(\displaystyle \text{Area of Parallelogram}=3 \times 1\)

\(\displaystyle \text{Area of Parallelogram}=3\)

Now, we are ready to find the area of the shaded region by subtracting the area of the parallelogram from the area of the rectangle.

\(\displaystyle \text{Area of Shaded Region}=\text{Area of Rectangle}-\text{Area of Parallelogram}\)

\(\displaystyle \text{Area of Shaded Region}=12-3\)

Solve.

\(\displaystyle \text{Area of Shaded Region}=9\)

Example Question #1 : How To Find The Area Of A Parallelogram

If the height of the parallelogram is half of the length of the rectangle, then find the area of the shaded region in the figure.

3

Possible Answers:

\(\displaystyle 32\)

\(\displaystyle 24\)

\(\displaystyle 16\)

\(\displaystyle 40\)

Correct answer:

\(\displaystyle 32\)

Explanation:

13

In order to find the area of the shaded region, we must first find the areas of the rectangle and parallelogram.

Recall how to find the area of a rectangle:

\(\displaystyle \text{Area of Rectangle}=\text{length}\times\text{width}\)

Substitute in the given length and height to find the area of the rectangle.

\(\displaystyle \text{Area of Rectangle}=4 \times 12\)

\(\displaystyle \text{Area of Rectangle}=48\)

Next, find the area of the parallelogram.

Recall how to find the area of a parallelogram:

\(\displaystyle \text{Area of Parallelogram}=\text{base}\times\text{height}\)

We need to find the height of the parallelogram. From the question, we know the following relationship:

\(\displaystyle \text{height}=\frac{\text{length}}{2}\)

Substitute in the length of the rectangle to find the height of the parallelogram.

\(\displaystyle \text{height}=\frac{4}{2}\)

\(\displaystyle \text{height}=2\)

Now, substitute in the height and the given length of the base to find the area of the parallelogram.

\(\displaystyle \text{Area of Parallelogram}=8 \times 2\)

\(\displaystyle \text{Area of Parallelogram}=16\)

Now, we are ready to find the area of the shaded region by subtracting the area of the parallelogram from the area of the rectangle.

\(\displaystyle \text{Area of Shaded Region}=\text{Area of Rectangle}-\text{Area of Parallelogram}\)

\(\displaystyle \text{Area of Shaded Region}=48-16\)

Solve.

\(\displaystyle \text{Area of Shaded Region}=32\)

Example Question #10 : How To Find The Area Of A Parallelogram

If the height of the parallelogram is half of the length of the rectangle, then find the area of the shaded region in the figure.

4

Possible Answers:

\(\displaystyle 180\)

\(\displaystyle 120\)

\(\displaystyle 90\)

\(\displaystyle 150\)

Correct answer:

\(\displaystyle 150\)

Explanation:

13

In order to find the area of the shaded region, we must first find the areas of the rectangle and parallelogram.

Recall how to find the area of a rectangle:

\(\displaystyle \text{Area of Rectangle}=\text{length}\times\text{width}\)

Substitute in the given length and height to find the area of the rectangle.

\(\displaystyle \text{Area of Rectangle}=12 \times 20\)

\(\displaystyle \text{Area of Rectangle}=240\)

Next, find the area of the parallelogram.

Recall how to find the area of a parallelogram:

\(\displaystyle \text{Area of Parallelogram}=\text{base}\times\text{height}\)

We need to find the height of the parallelogram. From the question, we know the following relationship:

\(\displaystyle \text{height}=\frac{\text{length}}{2}\)

Substitute in the length of the rectangle to find the height of the parallelogram.

\(\displaystyle \text{height}=\frac{12}{2}\)

\(\displaystyle \text{height}=6\)

Now, substitute in the height and the given length of the base to find the area of the parallelogram.

\(\displaystyle \text{Area of Parallelogram}=15 \times 6\)

\(\displaystyle \text{Area of Parallelogram}=\90\)

Now, we are ready to find the area of the shaded region by subtracting the area of the parallelogram from the area of the rectangle.

\(\displaystyle \text{Area of Shaded Region}=\text{Area of Rectangle}-\text{Area of Parallelogram}\)

\(\displaystyle \text{Area of Shaded Region}=240-90\)

Solve.

\(\displaystyle \text{Area of Shaded Region}=150\)

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