Examples with solutions for Area of a Deltoid: Using variables

Exercise #1

Given the deltoid ABCD

The main diagonal is equal to 2a+2

Secondary diagonal is equal to a

The area of the deltoid equals 6a

Calculate a a

S=6aS=6aS=6a2a+22a+22a+2aaaAAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve the question, we first need to remember the formula for the area of a kite:

Diagonal * Diagonal / 2

This means that if we substitute the given data we can see that:

a(2a+2)/2 = area of the kite

Let's remember that we are also given the area, so we'll put that in the equation too

a(2a+2)/2 = 6a

Now we have an equation that we can easily solve.

First, let's get rid of the fraction, so we'll multiply both sides of the equation by 2

a(2a+2)=6a*2
a(2a+2)=12a

Let's expand the parentheses on the left side of the equation

2a²+2a=12a

2a²=10a

Let's divide both sides of the equation by a

2a=10

Let's divide again by 2

a=5

And that's the solution!

Answer

5 cm

Exercise #2

Shown below is the deltoid ABCD.

The diagonal AC = X

Diagonal DB = 5

The area of the deltoid is 20 cm².

Calculate X.

S=20S=20S=20XXX555AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To calculate X X , follow these steps:

  • Step 1: Use the area formula for a deltoid Area=12×d1×d2 \text{Area} = \frac{1}{2} \times d_1 \times d_2 .
  • Step 2: Given the area =20cm2 = 20 \, \text{cm}^2 , d1=X d_1 = X , and d2=5 d_2 = 5 , substitute these into the formula.
  • Step 3: Set the equation: 20=12×X×5 20 = \frac{1}{2} \times X \times 5 .
  • Step 4: Simplify and solve for X X .

Now, let's solve:

Start with the equation 20=12×X×5 20 = \frac{1}{2} \times X \times 5 .

This simplifies to 20=5X2 20 = \frac{5X}{2} .

Multiply both sides by 2 to eliminate the fraction:

40=5X 40 = 5X .

Divide both sides by 5:

X=405 X = \frac{40}{5} .

Simplifying gives us X=8 X = 8 .

Therefore, the length of diagonal AC AC is X=8cm X = 8 \, \text{cm} .

Answer

x=8

Exercise #3

Shown below is the deltoid ABCD.

AC = 2X

DB = X

The area of the deltoid is equal to 32 cm².

Calculate DB.

S=32S=32S=322X2X2XXXXAAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve this problem, we will utilize the formula for the area of a deltoid, which is 12×AC×DB \frac{1}{2} \times AC \times DB . Given:

  • Diagonal AC=2X AC = 2X
  • Diagonal DB=X DB = X
  • Area = 32cm2 32 \, \text{cm}^2

The formula for the area of the deltoid is:

Area=12×AC×DB \text{Area} = \frac{1}{2} \times AC \times DB

Substitute the given values into the formula:

32=12×2X×X 32 = \frac{1}{2} \times 2X \times X

Simplify the equation:

32=12×2X2 32 = \frac{1}{2} \times 2X^2

32=X2 32 = X^2

Solve for X X by taking the square root of both sides:

X=32 X = \sqrt{32}

Since DB=X DB = X , the length of diagonal DB DB is 32\sqrt{32} .

Thus, the solution to the problem is 32\sqrt{32}.

Answer

32 \sqrt{32}

Exercise #4

The deltoid ABCD is shown below.

AC = X

DB = 3X

The area of the deltoid is 27 cm².

Calculate the length of AC.

S=27S=27S=27XXX3X3X3XAAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve this problem, we'll use the formula relating the area of a deltoid to its diagonals:

  • Step 1: Identify the given details:
    • Diagonal AC = X X .
    • Diagonal DB = 3X 3X .
    • Area = 27 cm2^2.
  • Step 2: Write down the formula for the area:
  • The area of a deltoid is given by:

    Area=12×AC×DB \text{Area} = \frac{1}{2} \times AC \times DB

  • Step 3: Substitute the values into the formula:
  • Substitute AC=X AC = X and DB=3X DB = 3X into the equation:

    12×X×3X=27 \frac{1}{2} \times X \times 3X = 27

  • Step 4: Simplify and solve for X X :
  • First, simplify the left side:

    12×3X2=32X2 \frac{1}{2} \times 3X^2 = \frac{3}{2}X^2

    Thus, the equation becomes:

    32X2=27 \frac{3}{2}X^2 = 27

    Multiply both sides by 2 to clear the fraction:

    3X2=54 3X^2 = 54

    Divide both sides by 3:

    X2=18 X^2 = 18

    Take the square root of both sides:

    X=18 X = \sqrt{18}

Therefore, the length of diagonal AC is 18 \sqrt{18} .

Answer

18 \sqrt{18}

Exercise #5

Shown below is the deltoid ABCD.

Side length BD equals 5 cm.

The area of the deltoid is 45 cm².

What is the the value of a? a? 555aaa3a3a3aAAABBBCCCDDDMMMS=45

Video Solution

Step-by-Step Solution

Let's solve this problem by working through the steps:

We are given a deltoid ABCD where:

  • The length of diagonal BD is 5 cm.
  • The sum of the segments forming diagonal AC is a+3a=4a a + 3a = 4a .
  • The area of the deltoid is 45 cm².

We use the area formula for a deltoid when the diagonals intersect at right angles:

Area=12×d1×d2 \text{Area} = \frac{1}{2} \times d_1 \times d_2

Here, d1=5 d_1 = 5 cm and d2=4a d_2 = 4a . Substituting these values into the formula:

12×5×4a=45 \frac{1}{2} \times 5 \times 4a = 45

Simplifying this equation:

12×20a=45 \frac{1}{2} \times 20a = 45

10a=45 10a = 45

Now, solve for a a :

a=4510 a = \frac{45}{10}

a=4.5 a = 4.5

Therefore, the length of segment a a is 4.5cm 4.5 \, \text{cm} .

Answer

4.5 4.5

Exercise #6

Given the deltoid ABCD

Side length AC equals 7 cm

The area of the deltoid is equal to 252 cm².

Find the value of the parameter a a S=252S=252S=2527779a9a9aAAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve this problem, we will calculate the value of a a using the given area of the deltoid and the known diagonal AC.

The formula for the area of a deltoid (kite) is:

Area=12×d1×d2 \text{Area} = \frac{1}{2} \times d_1 \times d_2

Here, d1=AC=7 d_1 = AC = 7 cm, and d2=BD=9a d_2 = BD = 9a cm. The area S=252 S = 252 cm².

Substitute the known values into the area formula:

252=12×7×9a 252 = \frac{1}{2} \times 7 \times 9a

Simplify and solve for a a :

252=632×a 252 = \frac{63}{2} \times a

252=31.5a 252 = 31.5a

a=25231.5 a = \frac{252}{31.5}

a=8 a = 8

Therefore, the value of the parameter a a is 8 8 .

Answer

8 8

Exercise #7

Look at the deltoid ABCD.

The side BD is 13 cm long.

The area of the deltoid is 182 cm².

Calculate a. a\text{.} S=182S=182S=1827a7a7a131313AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Use the formula for the area of a deltoid.
  • Step 2: Set up the equation using given values.
  • Step 3: Solve for the variable a a .

Let's go through each step:
Step 1: For a deltoid, the area A A can be calculated using:
A=12×AC×BD A = \frac{1}{2} \times AC \times BD

Step 2: Substituting the known values into the expression gives us:
182=12×7a×13 182 = \frac{1}{2} \times 7a \times 13

Step 3: Simplify and solve for a a :
We first find 12×13=6.5 \frac{1}{2} \times 13 = 6.5 , so:
182=6.5×7a 182 = 6.5 \times 7a
Solving for a a , we have:
182=45.5a 182 = 45.5a
a=18245.5=4 a = \frac{182}{45.5} = 4

Therefore, the solution to the problem is a=4 a = 4 .

Answer

4 4

Exercise #8

ABCD is a deltoid.

Side BM equals 4 cm.

The area of the deltoid is equal to 144 cm².

Calculate b.

2b2b2b4b4b4b444AAABBBCCCDDDMMMS=144

Video Solution

Step-by-Step Solution

To solve the problem, we'll follow the steps outlined:

  • Step 1: Identify the given information.
  • Step 2: Apply the appropriate formula for the area of the deltoid.
  • Step 3: Solve for b b in terms of known values.

Let's break it down:

Step 1: We know the length of diagonal BM=4 BM = 4 cm and the area of the deltoid is 144 144 cm².

Step 2: The area of a deltoid is given by the formula:

Area=12×Diagonal1×Diagonal2 \text{Area} = \frac{1}{2} \times \text{Diagonal}_1 \times \text{Diagonal}_2

Here, the diagonals correspond to line segments of the form 2b 2b and 4b 4b as represented in the setup of the problem.

Step 3: Substituting the values into the area formula, we have:

12×(2b)×(4b)=144 \frac{1}{2} \times (2b) \times (4b) = 144

Simplifying this, we get:

4b2=144b2=1444=36 4b^2 = 144 \quad \Rightarrow \quad b^2 = \frac{144}{4} = 36

Therefore, solving for b b , we find:

b=36=6 b = \sqrt{36} = 6

Thus, the value of b b is 6 6 .

Answer

6 6

Exercise #9

Below is the deltoid ABCD.

Side length BD equals 7 cm.

The area of the deltoid is equal to 98 cm².

What is the value of a? a\text{?} 7772a2a2a5a5a5aAAABBBCCCDDDMMMS=98

Video Solution

Answer

4 4

Exercise #10

Given the deltoid ABCD

Side length BD equals 8 cm

The area of the deltoid is equal to 180 cm².

Find the value of the parameter a a 8882a2a2a7a7a7aAAABBBCCCDDDMMMS=180

Video Solution

Answer

5 5

Exercise #11

Given the deltoid ABCD

height AE formed by the diagonal extension AC

Side length ED equals 3 cm

The area of the deltoid is equal to 189 cm².

Find the value of the parameter

S=189S=189S=1897b7b7b333AAABBBCCCDDDEEE

Video Solution

Answer

9 9

Exercise #12

Shown below is the deltoid ABCD.

Side length MD equals 3 cm.

The area of the deltoid is 180 cm².

What is the value of b? b\text{?} bbb3b3b3b333AAABBBCCCDDDMMMS=180

Video Solution

Answer

15 15

Exercise #13

Given the deltoid ABCD

Side length MD equals 2 cm

The area of the deltoid is equal to 200 cm².

Find the value of the parameter b b 2b2b2b3b3b3b222AAABBBCCCDDDMMMS=200

Video Solution

Answer

20 20

Exercise #14

Given the deltoid ABCD

height AE formed by the diagonal extension AC

Side BE equals 5 cm

The area of the deltoid is equal to 160 cm².

Find the value of the parameter b b S=160S=160S=1604b4b4b555AAABBBCCCDDDEEE

Video Solution

Answer

8 8