Examples with solutions for Area of a Deltoid: Calculate The Missing Side based on the formula

Exercise #1

The deltoid below has an area of 60 cm².

888XXX

What is the value of X?

Video Solution

Step-by-Step Solution

To solve the problem, we need to remember the formula for the area of a rhombus:

The product of the diagonals multiplied together and then divided by 2.

Let's substitute in our data into the formula:

(8*X) = 60
2

Note that we can simplify the fraction, thus eliminating the denominator:

4X = 60

Let's finally divide the equation by 4 to get our answer:

X = 15

Answer

15

Exercise #2

The kite ABCD shown below has an area of 42 cm².

AB = BC

DC = AD

BD = 14

The diagonals of the kite intersect at point 0.

Calculate the length of side AO.

S=42S=42S=42141414DDDAAABBBCCCOOO

Video Solution

Step-by-Step Solution

We substitute the data we have into the formula for the area of the kite:

S=AC×BD2 S=\frac{AC\times BD}{2}

42=AC×142 42=\frac{AC\times14}{2}

We multiply by 2 to remove the denominator:

 14AC=84 14AC=84

Then divide by 14:

AC=6 AC=6

In a rhombus, the main diagonal crosses the second diagonal, therefore:

AO=AC2=62=3 AO=\frac{AC}{2}=\frac{6}{2}=3

Answer

3 cm

Exercise #3

Given the deltoid ABCD

Side length BD equals 4 cm

The area of the deltoid is equal to 20 cm².

Find the length of the side AC

S=20S=20S=20444AAADDDCCCBBB

Video Solution

Step-by-Step Solution

To solve for the length of side AC AC in the deltoid ABCD ABCD , we will use the deltoid area formula:

The formula for the area of a deltoid is given by Area=12×d1×d2 \text{Area} = \frac{1}{2} \times d_1 \times d_2 , where d1 d_1 and d2 d_2 are the lengths of the diagonals.

Given:

  • The area of the deltoid: Area=20cm2 \text{Area} = 20 \, \text{cm}^2
  • The length of diagonal BD=4cm BD = 4 \, \text{cm} .
  • We need to find the length of diagonal AC AC .

Substitute the known values into the formula:

20=12×AC×4 20 = \frac{1}{2} \times AC \times 4

Re-arrange the equation to solve for AC AC :

20=2×AC 20 = 2 \times AC

Divide both sides by 2:

AC=202=10cm AC = \frac{20}{2} = 10 \, \text{cm}

Thus, the length of side AC AC is 10cm 10 \, \text{cm} .

The only choice matching this calculation is:

:

10 10 cm

Answer

10 10 cm

Exercise #4

Given the deltoid ABCD

Side length AC equals 10 cm

The area of the deltoid is equal to 40 cm².

Find the length of the side BD

S=40S=40S=40101010AAABBBCCCDDD

Video Solution

Step-by-Step Solution

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

  • Step 1: Utilize the formula for the area of a kite or deltoid, S=12d1d2 S = \frac{1}{2} \cdot d_1 \cdot d_2 .
  • Step 2: Substituting the known values into this formula.
  • Step 3: Solve for the unknown diagonal BDBD.

Now, let's work through each step:
Step 1: The given side ACAC acts as the first diagonal d1=10d_1 = 10 cm. The area S=40S = 40 cm².
Step 2: Plug these values into the formula S=12d1d2 S = \frac{1}{2} \cdot d_1 \cdot d_2 which becomes 40=1210BD 40 = \frac{1}{2} \cdot 10 \cdot BD .
Step 3: Solving for BDBD involves rearranging the equation: 40=1210BD    40=5BD    BD=405=8 cm 40 = \frac{1}{2} \cdot 10 \cdot BD \implies 40 = 5 \cdot BD \implies BD = \frac{40}{5} = 8 \text{ cm}

Therefore, the length of the side BDBD is 8 cm 8 \text{ cm} .

Answer

8 8 cm

Exercise #5

Given the deltoid ABCD

Side length BD equals 6 cm

The area of the deltoid is equal to 54 cm².

Find the length of the side AC

S=54S=54S=54666AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To find the length of side AC AC , follow these steps:

  • Step 1: Use the formula for the area of a deltoid: Area=12×d1×d2 \text{Area} = \frac{1}{2} \times d_1 \times d_2 .
  • Step 2: Set the known values into the equation, where d1=BD=6 d_1 = BD = 6 cm and the area is 54 cm2^2.
  • Step 3: Rearrange the formula to solve for d2 d_2 (which is AC AC ): 54=12×6×AC 54 = \frac{1}{2} \times 6 \times AC .
  • Step 4: Simplify and solve for AC AC : 54=3×AC 54 = 3 \times AC .
  • Step 5: Divide both sides by 3 to isolate AC AC : AC=543=18 AC = \frac{54}{3} = 18 cm.

Therefore, the length of AC AC is 18 18 cm.

Answer

18 18 cm

Exercise #6

Given the deltoid ABCD

Side length AC equals 9 cm

The area of the deltoid is equal to 72 cm².

Find the length of the side BD

S=72S=72S=72999AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve this problem, we will compute the length of diagonal BD using the formula for the area of a deltoid:

  • Step 1: Recall the formula for the area of a deltoid, which is given by:
  • Area=12×AC×BD \text{Area} = \frac{1}{2} \times AC \times BD
  • Step 2: Substitute the known values into the formula:
  • 72=12×9×BD 72 = \frac{1}{2} \times 9 \times BD
  • Step 3: Solve the equation for BD:
  • First, multiply both sides of the equation by 2 to clear the fraction:

    144=9×BD 144 = 9 \times BD

    Next, divide both sides by 9 to isolate BD:

    BD=1449 BD = \frac{144}{9}
  • Step 4: Perform the division:
  • BD=16 BD = 16

Thus, the length of diagonal BD is 16 16 cm.

This conclusion matches the possible answer choice 4:

The correct choice is (4): 16 16 cm.

Answer

16 16 cm

Exercise #7

Given the deltoid ABCD

Side length AC equals 11 cm

The area of the deltoid is equal to 44 cm².

Find the length of the side BD

S=44S=44S=44111111AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve this problem, we'll use the formula for the area of a deltoid:

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

Let's work through the steps:

Step 1: Write down the formula for the area of the deltoid. The area S S is given as:

44=12×11×BD 44 = \frac{1}{2} \times 11 \times BD

Step 2: Rearrange this equation to solve for the unknown diagonal BD BD :

44×2=11×BD 44 \times 2 = 11 \times BD

88=11×BD 88 = 11 \times BD

Step 3: Divide both sides by 11 to find the length of BD BD :

BD=8811=8 BD = \frac{88}{11} = 8 cm

Therefore, the solution to the problem is BD=8 BD = 8 cm.

Answer

8 8 cm

Exercise #8

Given the deltoid ABCD

Side length BD equals 7 cm

The area of the deltoid is equal to 49 cm².

Find the length of the side AC

S=49S=49S=49777AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve for the length of side AC in the deltoid:

  • Step 1: Identify the formula for the area, which is given by:
    Area=12×BD×AC \text{Area} = \frac{1}{2} \times BD \times AC where BDBD and ACAC are the diagonals.
  • Step 2: Substitute known values into the formula:
    Given that BD=7cmBD = 7\, \text{cm} and Area=49cm2\text{Area} = 49\, \text{cm}^2, we have:
    49=12×7×AC 49 = \frac{1}{2} \times 7 \times AC
  • Step 3: Solve the equation for ACAC:
    Multiply both sides of the equation by 2 to eliminate the fraction:
    98=7×AC 98 = 7 \times AC Divide both sides by 7:
    AC=987=14 AC = \frac{98}{7} = 14

Therefore, the length of the side ACAC is 14cm 14 \, \text{cm} .

Answer

14 14 cm

Exercise #9

Given the deltoid ABCD

Side length AC equals 13 cm

The area of the deltoid is equal to 39 cm².

Find the length of the side BD

S=39S=39S=39131313AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To find the length of diagonal BD BD , we will apply the formula for the area of a deltoid:

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

In this problem, Diagonal 1 is AC=13 AC = 13 cm, and Diagonal 2 is BD BD , which we are trying to find. The area is given as 39 39 cm². Substituting these values into the formula, we get:

39=12×13×BD39 = \frac{1}{2} \times 13 \times BD

To solve for BD BD , multiply both sides by 2 to eliminate the fraction:

78=13×BD78 = 13 \times BD

Now, solve for BD BD by dividing both sides by 13:

BD=7813BD = \frac{78}{13}

Simplify to find:

BD=6BD = 6

Therefore, the length of diagonal BD BD is 6 6 cm.

Answer

6 6 cm

Exercise #10

Given ABCD deltoid AD=AB CB=CD

The diagonals of the deltoid intersect at the point O

Given in cm AO=6 BO=5

The area of the deltoid is equal to 80 cm².

Calculate the side CO

S=80S=80S=80666555DDDAAABBBCCCOOO

Video Solution

Step-by-Step Solution

To solve for COCO, we will use the area formula for the deltoid:

  • Step 1: Calculate full length of diagonal BDBD:

BD=2×BO=2×5=10 cmBD = 2 \times BO = 2 \times 5 = 10 \text{ cm}.

  • Step 2: Use the kite area formula:

  • Area=12ACBD\text{Area} = \frac{1}{2} \cdot AC \cdot BD.

Substitute known values into the formula:

80=12(6+CO)1080 = \frac{1}{2} \cdot (6 + CO) \cdot 10.

Step 3: Simplify and solve for COCO:

80=5(6+CO)80 = 5 \cdot (6 + CO) leads to

80=30+5CO80 = 30 + 5CO.

Solving for COCO, we subtract 30 from both sides:

50=5CO 50 = 5CO ,

CO=505=10 CO = \frac{50}{5} = 10 .

Therefore, the side COCO is 10 cm.

Answer

10

Exercise #11

The deltoid ABCD is shown below.

Side length AC equals 6 cm.

The area of the deltoid is 48 cm².

What is the length of the side BD?

S=48S=48S=48666AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve for BD BD , the diagonal of the deltoid, follow these steps:

  • Step 1: Recognize that the area of a deltoid with perpendicular diagonals is given by the formula A=12×d1×d2 A = \frac{1}{2} \times d_1 \times d_2 .
  • Step 2: Substitute the known values into the formula: 48=12×6×BD 48 = \frac{1}{2} \times 6 \times BD .
  • Step 3: Simplify and solve for BD BD :

Substituting AC=6 AC = 6 cm, we have:

48=12×6×BD 48 = \frac{1}{2} \times 6 \times BD

Multiply both sides by 2 to clear the fraction:

96=6×BD 96 = 6 \times BD

Divide both sides by 6 to solve for BD BD :

BD=966=16 BD = \frac{96}{6} = 16 cm

Thus, the length of BD BD is 16 16 cm.

Answer

16 16 cm

Exercise #12

Given the deltoid ABCD

Side length BD equals 12 cm

The area of the deltoid is equal to 60 cm².

Find the length of the side AC

S=60S=60S=60121212AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To find the length of side AC AC in the given deltoid:

  • Step 1: Write down the area formula for a kite: S=12×BD×AC S = \frac{1}{2} \times BD \times AC , where S S is the area, and BD BD and AC AC are the diagonals.
  • Step 2: Plug in the known values: 60=12×12×AC 60 = \frac{1}{2} \times 12 \times AC .
  • Step 3: Simplify the equation: 60=6×AC 60 = 6 \times AC .
  • Step 4: Solve for AC AC :

AC=606=10 AC = \frac{60}{6} = 10 cm.

Therefore, the length of side AC AC is 10 10 cm.

Answer

10 10 cm

Exercise #13

Given the deltoid ABCD

Side length AC equals 8 cm

The area of the deltoid is equal to 64 cm².

Find the length of the side BD

S=64S=64S=64888AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve the problem of finding the length of the diagonal BD BD in deltoid ABCD ABCD , where AC=8cm AC = 8 \, \text{cm} and the area S=64cm2 S = 64 \, \text{cm}^2 , follow these steps:

  • Step 1: Identify the given values: AC=8cm AC = 8 \, \text{cm} and S=64cm2 S = 64 \, \text{cm}^2 .
  • Step 2: Apply the area formula for a deltoid: S=12×AC×BD S = \frac{1}{2} \times AC \times BD .
  • Step 3: Substitute the known values into the formula.
  • Step 4: Solve for BD BD .

Now, let's work through the calculation:

Given the formula for the area of a deltoid: S=12×AC×BD S = \frac{1}{2} \times AC \times BD

Substitute the known values: 64=12×8×BD 64 = \frac{1}{2} \times 8 \times BD

To solve for BD BD , first multiply both sides by 2 to get rid of the fraction: 128=8×BD 128 = 8 \times BD

Now, divide both sides by 8 to isolate BD BD : BD=1288=16 BD = \frac{128}{8} = 16

Therefore, the length of BD BD is 16 cm \textbf{16 cm} .

Answer

16 16 cm

Exercise #14

Given the deltoid ABCD

Side length AC equal to 5.5 cm

The area of the deltoid is equal to 27.5 cm².

Find the length of the side BD

S=27.5S=27.5S=27.55.55.55.5AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve this problem, we'll proceed as follows:

  • Step 1: Identify given information and formula to use: The area of a deltoid is given as Area=12×d1×d2 \text{Area} = \frac{1}{2} \times d_1 \times d_2 .
  • Step 2: Plug in the known values: 27.5=12×5.5×BD 27.5 = \frac{1}{2} \times 5.5 \times BD .
  • Step 3: Calculate the unknown length BD BD .

Now, let's work through each step:

Step 1: Given Area=27.5 \text{Area} = 27.5 cm2^2, AC=5.5 AC = 5.5 cm, and the formula for the area of a deltoid: Area=12×d1×d2 \text{Area} = \frac{1}{2} \times d_1 \times d_2 where d1=AC d_1 = AC and d2=BD d_2 = BD .

Step 2: Use the formula with the given values:
27.5=12×5.5×BD 27.5 = \frac{1}{2} \times 5.5 \times BD .

Step 3: Solve for BD BD :
Multiply both sides by 2 to eliminate the fraction:
55=5.5×BD 55 = 5.5 \times BD .
Now, divide both sides by 5.5 5.5 :
BD=555.5 BD = \frac{55}{5.5} .

Simplify 555.5 \frac{55}{5.5} :
BD=10 BD = 10 cm.

Therefore, the length of side BD BD is 10 10 cm.

Answer

10 10 cm

Exercise #15

Below is the deltoid ABCD.

Side length BD equals 15 cm.

The area of the deltoid is 60 cm².

Find the length of the side AC.

S=60S=60S=60151515AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve this problem, we'll apply the following steps:

  • Step 1: Identify the given information: BD=15BD = 15 cm and the area is 6060 cm².

  • Step 2: Use the formula for the area of a deltoid.

  • Step 3: Solve for the unknown diagonal ACAC.

Now, let's work through each step:
Step 1: We know the area formula for a deltoid is given by: Area=12×AC×BD \text{Area} = \frac{1}{2} \times AC \times BD

Step 2: Substitute the given values into the formula: 60=12×AC×15 60 = \frac{1}{2} \times AC \times 15

Step 3: Simplify and solve for ACAC: 60=152×AC 60 = \frac{15}{2} \times AC
Multiply both sides by 2 to isolate ACAC: 120=15×AC 120 = 15 \times AC
Divide both sides by 15: AC=12015=8 AC = \frac{120}{15} = 8

Therefore, the length of the side ACAC is 8 8 cm.

Answer

8 8 cm

Exercise #16

Given below is the deltoid ABCD.

Side length MD equals 3 cm.

The area of the deltoid is 72 cm².

What is the length of the side AC?

333AAABBBCCCDDDMMMS=72

Video Solution

Step-by-Step Solution

To solve for the length of AC AC in the deltoid:

  • Given MD=3 MD = 3 cm, which implies BD=2×MD=6 BD = 2 \times MD = 6 cm.
  • The area of the deltoid is given by the formula: Area=12×AC×BD \text{Area} = \frac{1}{2} \times AC \times BD .

Putting the known values into the formula:
72=12×AC×6 72 = \frac{1}{2} \times AC \times 6 .

To isolate AC AC , multiply both sides by 2:

144=AC×6 144 = AC \times 6 .

Divide both sides by 6 to solve for AC AC :

AC=1446=24cm AC = \frac{144}{6} = 24 \, \text{cm} .

Therefore, the length of the side AC AC is 24cm 24 \, \text{cm} .

Answer

24 24 cm

Exercise #17

Shown below is the deltoid ABCD.

Side length BM equals 2 cm.

The area of the deltoid is 72 cm².

Find the length of the side AC.

AAABBBCCCDDDMMMS=72

Video Solution

Step-by-Step Solution

To solve this problem, we'll employ the formula for the area of a kite or deltoid, which relates to its diagonals AC and BD.

The formula is:

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

Given that the diagonal BD consists of BM and MD, and BM = MD as M is the midpoint, we have:

d2=BD=BM+MD=2+2=4 cm d2 = BD = BM + MD = 2 + 2 = 4 \text{ cm}

Also, the area is given as 72 cm². We substitute into the area formula:

72=12×AC×4 72 = \frac{1}{2} \times AC \times 4

Simplifying the equation by multiplying through by 2 to eliminate the fraction:

144=AC×4 144 = AC \times 4

Divide both sides by 4 to solve for AC:

AC=1444 AC = \frac{144}{4}

Therefore:

AC=36 cm AC = 36 \text{ cm}

Thus, the length of side AC is 36 cm \textbf{36 cm} .

Answer

36 36 cm

Exercise #18

Shown below is the deltoid ABCD.

DB = 4

The area of the deltoid is 28 cm².

Calculate the length of side AC.

S=28S=28S=28444AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To calculate the length of the diagonal AC AC , we start by using the area formula for a deltoid, which involves its diagonals. The area A A of a deltoid is given by:

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

Given:

  • The area of the deltoid A=28cm2 A = 28 \, \text{cm}^2 .
  • The length of diagonal DB=4cm DB = 4 \, \text{cm} .

We can plug these values into the formula:

28=12×AC×4 28 = \frac{1}{2} \times AC \times 4

Solving for AC AC :

28=2×AC 28 = 2 \times AC

Divide both sides by 2 2 :

AC=282=14 AC = \frac{28}{2} = 14

Therefore, the length of side AC AC is 14 cm.

Answer

14 cm²

Exercise #19

Given the deltoid ABCD

DB=4 the area of the deltoid is equal to 32 cm².

Calculate the side AC

S=32S=32S=32444AAABBBCCCDDD

Video Solution

Step-by-Step Solution

To solve for AC AC in the deltoid, use the area formula:

  • Step 1: The area of a deltoid is given by A=12×p×q A = \frac{1}{2} \times p \times q , where p p and q q are diagonals.
  • Step 2: For this problem, set p=DB=4 p = DB = 4 cm, and q=AC q = AC (unknown).
  • Step 3: Substitute the values: 32=12×4×AC 32 = \frac{1}{2} \times 4 \times AC .

Now, solve for AC AC :
32=12×4×AC 32 = \frac{1}{2} \times 4 \times AC
32=2×AC 32 = 2 \times AC
Divide both sides by 2:
AC=322=16cm AC = \frac{32}{2} = 16 \, \text{cm}

The side AC AC is therefore 16 cm.

Answer

16 cm

Exercise #20

Below is the deltoid ABCD.

C = 8

The area of the deltoid is equal to 32 cm².

Calculate the side DB.

S=32S=32S=32888AAABBBCCCDDD

Video Solution

Step-by-Step Solution

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

  • Step 1: Set up the equation using the area of the deltoid formula.
  • Step 2: Substitute the known values and solve for the unknown diagonal DB DB .

Here's the step-by-step solution:

Step 1: The area of a deltoid can be calculated using the formula:
Area=12×d1×d2 \text{Area} = \frac{1}{2} \times d_1 \times d_2
Given that Area=32 \text{Area} = 32 cm² and d1=AC=8 d_1 = AC = 8 cm, we place these values into the equation:

Step 2: Substitute into the formula:
32=12×8×DB 32 = \frac{1}{2} \times 8 \times DB

Step 3: Simplify the equation:
32=4×DB 32 = 4 \times DB

Step 4: Solve for DB DB :
DB=324=8 DB = \frac{32}{4} = 8

Therefore, the length of diagonal DB DB is 8 cm.

Answer

8 cm