Pre-Algebra : Area of a Parallelogram

Study concepts, example questions & explanations for Pre-Algebra

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Area Of A Parallelogram

What is the area of the parallelogram?

Problem_12

Possible Answers:

\(\displaystyle 28\)

\(\displaystyle 24\)

\(\displaystyle 20\)

\(\displaystyle 35\)

Correct answer:

\(\displaystyle 28\)

Explanation:

The area of a parallelogram is determined using the equation:

\(\displaystyle A=bh\)

In this problem:

\(\displaystyle A=(7)(4)=28\)

Example Question #2 : Area Of A Parallelogram

Parallelogram

Refer to the above figure, which shows Parallelogram \(\displaystyle ABCD\). You are given that \(\displaystyle \overline{AX} \perp \overline{BC}\) and \(\displaystyle \overline{AY} \perp \overline{CD}\)

If you know the length of \(\displaystyle \overline{AD}\), then, of the following segments, choose the one whose length, if known, will allow us to calculate the area of Parallelogram \(\displaystyle ABCD\) .

Possible Answers:

\(\displaystyle \overline{CD}\)

\(\displaystyle \overline{AY}\)

\(\displaystyle \overline{AX}\)

\(\displaystyle \overline{AB}\)

\(\displaystyle \overline{BC}\)

Correct answer:

\(\displaystyle \overline{AX}\)

Explanation:

The area of a parallelogram is the product of the length of any one side, or its base, and the perpendicular distance to the opposite side, or its height. If we know \(\displaystyle \overline{AD}\), then we also know \(\displaystyle \overline{BC}\), which is of the same length. We can take \(\displaystyle \overline{BC}\) to be the base, and the segement perpendicular to it, \(\displaystyle \overline{AX}\), as the altitude. Therefore, \(\displaystyle \overline{AX}\) is the segment whose length we need to know.

Example Question #1 : Area Of A Parallelogram

Parallelogram

Note: Figure NOT drawn to scale.

Refer to the above figure, which shows Parallelogram \(\displaystyle ABCD\). You are given that \(\displaystyle \overline{AX} \perp \overline{BC}\) and \(\displaystyle \overline{AY} \perp \overline{CD}\)

\(\displaystyle AD = 100\)\(\displaystyle AB = 120\)\(\displaystyle AY = 80\)

Evaluate \(\displaystyle AX\).

Possible Answers:

\(\displaystyle AX = 96\)

\(\displaystyle AX = 150\)

\(\displaystyle AX = 60\)

\(\displaystyle AX = 140\)

\(\displaystyle AX = 66\frac{2}{3}\)

Correct answer:

\(\displaystyle AX = 96\)

Explanation:

The area of a parallelogram is the product of the length of any one side, or its base, and the length of a segment perpendicular to that side, or its height. 

One way to find the area is to multiply the length of side \(\displaystyle \overline{CD}\) by its corresponding altitude, \(\displaystyle \overline{AY}\). Since \(\displaystyle CD = AB = 120\) and \(\displaystyle AY = 80\)

\(\displaystyle A = (CD)(AY) = 120 \cdot 80 = 9,600\).

Another way to find the area is to multiply the length of side \(\displaystyle \overline{BC}\) by its corresponding altitude, \(\displaystyle \overline{AX}\). Since \(\displaystyle BC = AD= 100\) and the area is 9,600, we set up this equation and solve for \(\displaystyle AX\):

\(\displaystyle A = (BC)(AX)\)

\(\displaystyle 100 \cdot AX =9,600\)

\(\displaystyle AX = 96\)

Example Question #2 : Area Of A Parallelogram

A parallelogram has the base length of \(\displaystyle t\) and the altitude of \(\displaystyle 2t-1\). Give the area of the parallelogram.

Possible Answers:

\(\displaystyle t^2\)

\(\displaystyle 2t^2+t\)

\(\displaystyle 2t^2\)

\(\displaystyle 2t^2-t\)

\(\displaystyle t^2+t\)

Correct answer:

\(\displaystyle 2t^2-t\)

Explanation:

The area of a parallelogram is given by:

 

\(\displaystyle Area=ba\)

 

Where \(\displaystyle b\) is the base length and \(\displaystyle a\) is the corresponding altitude. So we can write:

 

\(\displaystyle Area=t(2t-1)=2t^2-t\)

Example Question #821 : Geometry

A parallelogram has a base length of \(\displaystyle t\) which is 3 times longer than its corresponding altitude. The area of the parallelogram is 12 square inches. Give the \(\displaystyle t\).

Possible Answers:

\(\displaystyle 6\)

\(\displaystyle 5\)

\(\displaystyle 4\)

\(\displaystyle 6\sqrt{3}\)

\(\displaystyle 6\sqrt{2}\)

Correct answer:

\(\displaystyle 6\)

Explanation:

Base length is \(\displaystyle t\) so the corresponding altitude is  \(\displaystyle \frac{t}{3}\).

 

The area of a parallelogram is given by:

 

\(\displaystyle Area=ba\)

 

Where:


\(\displaystyle b\) is the length of any base
\(\displaystyle a\) is the corresponding altitude

 

So we can write:

 

\(\displaystyle 12=t\times \frac{t}{3}\Rightarrow t\times t=12\times 3\Rightarrow t^2=36\Rightarrow t=6\)

\(\displaystyle t\times t=12\times 3\)

\(\displaystyle t^{2}=36\)

\(\displaystyle t=6\)

Example Question #822 : Geometry

The length of the shorter diagonal of a rhombus is 40% that of the longer diagonal. The area of the rhombus is \(\displaystyle K\). Give the length of the longer diagonal in terms of \(\displaystyle K\).

Possible Answers:

\(\displaystyle \sqrt{5K}\)

\(\displaystyle K\sqrt{\frac{5}{2}}\)

\(\displaystyle K\sqrt{\frac{2}{5}}\)

\(\displaystyle \frac{1}{5}\sqrt{K}\)

\(\displaystyle \sqrt{\frac{5K}{2}}\)

Correct answer:

\(\displaystyle \sqrt{5K}\)

Explanation:

Let \(\displaystyle D\) be the length of the longer diagonal. Then the shorter diagonal has length 40% of this. Since 40% is equal to \(\displaystyle \frac{40}{100 } = \frac{40 \div 20 }{100 \div 20 } = \frac{2}{5}\), 40% of \(\displaystyle D\) is equal to \(\displaystyle \frac{2}{5}D\).

The area of a rhombus is half the product of the lengths of its diagonals, so we can set up, and solve for \(\displaystyle D\), in the equation:

\(\displaystyle \frac{1}{2} \cdot \frac{2}{5}D \cdot D = K\)

\(\displaystyle \frac{1}{5}D^{2}= K\)

\(\displaystyle 5\cdot \frac{1}{5}D^{2}=5\cdot K\)

\(\displaystyle D^{2}=5K\)

\(\displaystyle D =\sqrt{5K}\)

 

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

The length of the shorter diagonal of a rhombus is two-thirds that of the longer diagonal. The area of the rhombus is \(\displaystyle Q\) square yards. Give the length of the longer diagonal, in inches, in terms of \(\displaystyle Q\).

Possible Answers:

\(\displaystyle 3\sqrt{ 3Q}\)

\(\displaystyle 4\sqrt{ 3Q}\)

\(\displaystyle \sqrt{ 3Q}\)

\(\displaystyle 12\sqrt{ 3Q}\)

\(\displaystyle 36\sqrt{ 3Q }\)

Correct answer:

\(\displaystyle 36\sqrt{ 3Q }\)

Explanation:

Let \(\displaystyle D\) be the length of the longer diagonal in yards. Then the shorter diagonal has length two-thirds of this, or \(\displaystyle \frac{2}{3}D\).

The area of a rhombus is half the product of the lengths of its diagonals, so we can set up the following equation and solve for \(\displaystyle D\):

\(\displaystyle \frac{1}{2} \cdot \frac{2}{3}D \cdot D = Q\)

\(\displaystyle \frac{1}{3}D ^{2} = Q\)

\(\displaystyle 3\cdot \frac{1}{3}D ^{2} = 3 \cdot Q\)

\(\displaystyle D ^{2} = 3Q\)

\(\displaystyle D = \sqrt{3Q}\)

To convert yards to inches, multiply by 36:

\(\displaystyle \sqrt{ 3Q } \times 36 = 36\sqrt{ 3Q }\)

Example Question #51 : Geometry

The longer diagonal of a rhombus is 20% longer than the shorter diagonal; the rhombus has area \(\displaystyle N\). Give the length of the shorter diagonal in terms of \(\displaystyle N\).

Possible Answers:

\(\displaystyle \sqrt{15N}\)

\(\displaystyle \sqrt{ \frac{3N}{5}}\)

\(\displaystyle \sqrt{ \frac{N}{5}}\)

\(\displaystyle \sqrt{ \frac{5N}{3}}\)

\(\displaystyle \sqrt{5N}\)

Correct answer:

\(\displaystyle \sqrt{ \frac{5N}{3}}\)

Explanation:

Let \(\displaystyle D\) be the length of the shorter diagonal. If the longer diagonal is 20% longer, then it measures 120% of the length of the shorter diagonal; this is 

\(\displaystyle \frac{120}{100} = \frac{120 \div 20}{100 \div 20} = \frac{6}{5}\)

of \(\displaystyle D\), or \(\displaystyle \frac{6}{5}D\).

The area of a rhombus is half the product of the lengths of its diagonals, so we can set up an equation and solve for \(\displaystyle D\):

\(\displaystyle \frac{1}{2} \cdot \frac{6}{5}D \cdot D = N\)

\(\displaystyle \frac{3}{5}D^{2} = N\)

\(\displaystyle \frac{5}{3} \cdot \frac{3}{5}D^{2} = \frac{5}{3} \cdot N\)

\(\displaystyle D^{2} = \frac{5N}{3}\)

\(\displaystyle D =\sqrt{ \frac{5N}{3}}\)

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

Find the area:

Question_5

 

Possible Answers:

\(\displaystyle \small 12\)

\(\displaystyle \small 32\)

\(\displaystyle \small 16\)

\(\displaystyle 15\)

\(\displaystyle \small 24\)

Correct answer:

\(\displaystyle \small 24\)

Explanation:

The area of a parallelogram can be determined using the following equation:

\(\displaystyle \small A=bh\)

Therefore,

\(\displaystyle \small A=8\times3=24\)

 

Example Question #1 : Area Of A Parallelogram

Find the area of a parallelogram with a base of length 8 and a height of length 6.

Possible Answers:

\(\displaystyle A=36\)

\(\displaystyle A=48\)

\(\displaystyle A=28\)

\(\displaystyle A=24\)

\(\displaystyle A=7\)

Correct answer:

\(\displaystyle A=48\)

Explanation:

The area of a parallelogram is \(\displaystyle A=bh=(base)(height)\)

\(\displaystyle A=(6)(8)=48\)

Learning Tools by Varsity Tutors