Deltoid ABCD: Calculate DB When AC is 75% of DB and Area is 108X cm²

Deltoid Area with Diagonal Relationships

Given the deltoid ABCD

Diagonal AC is equal to 75% of the diagonal DB

Area of the deltoid is equal to 108X cm².

Calculate the side DB,
if it was given that it is equal to X

AAABBBCCCDDD

❤️ Continue Your Math Journey!

We have hundreds of course questions with personalized recommendations + Account 100% premium

Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find side DB (X)
00:06 Side ratio according to the given data
00:17 Convert from percentage to fraction
00:22 Use the formula for calculating kite area
00:30 Product of diagonals divided by 2
00:34 Substitute appropriate values according to the data, and solve for X
00:50 Multiply by 2 to eliminate the fraction
00:59 Simplify what's possible
01:09 Isolate X
01:22 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given the deltoid ABCD

Diagonal AC is equal to 75% of the diagonal DB

Area of the deltoid is equal to 108X cm².

Calculate the side DB,
if it was given that it is equal to X

AAABBBCCCDDD

2

Step-by-step solution

To solve this problem, let's proceed through the steps:

Step 1: Formula for the Area of a Deltoid

The area of a deltoid can be calculated through its diagonals using the formula:

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

In this problem, the diagonals are ACAC and DBDB.

Step 2: Express ACAC in terms of DBDB

We are told that ACAC is 75%75\% of DBDB. Therefore:

AC=0.75×DB AC = 0.75 \times DB

Step 3: Substitute into the Area Formula

Substitute AC=0.75×DBAC = 0.75 \times DB into the area formula:

12×(0.75×DB)×DB=108X \frac{1}{2} \times (0.75 \times DB) \times DB = 108X

Simplifying gives:

0.375×DB2=108X 0.375 \times DB^2 = 108X

Step 4: Solve for DBDB

Substituting DB=XDB = X and rearranging the equation:

0.375×X2=108X 0.375 \times X^2 = 108X

Divide both sides by XX (assuming X0X \neq 0):

0.375X=108 0.375 X = 108

Solving for XX:

X=1080.375=288 X = \frac{108}{0.375} = 288

Thus, the length of diagonal DBDB is 288\boxed{288} cm.

3

Final Answer

288 cm²

Key Points to Remember

Essential concepts to master this topic
  • Formula: Area of deltoid = 12×d1×d2 \frac{1}{2} \times d_1 \times d_2
  • Technique: Express AC as 0.75 × DB, then substitute into area formula
  • Check: Area = 12×216×288=31,104 \frac{1}{2} \times 216 \times 288 = 31,104 when X = 288 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to use the diagonal relationship
    Don't set up the area formula as 12×AC×DB=108X \frac{1}{2} \times AC \times DB = 108X without expressing AC in terms of DB = you'll have two unknowns! This makes the equation unsolvable. Always substitute AC = 0.75 × DB first to create one equation with one unknown.

Practice Quiz

Test your knowledge with interactive questions

Indicate the correct answer

The next quadrilateral is:

AAABBBCCCDDD

FAQ

Everything you need to know about this question

What exactly is a deltoid and how is it different from other quadrilaterals?

+

A deltoid (also called a kite) is a quadrilateral with two pairs of adjacent sides that are equal. Unlike rectangles or squares, its diagonals are perpendicular and one bisects the other, which is why we can use the formula 12×d1×d2 \frac{1}{2} \times d_1 \times d_2 .

Why does AC being 75% of DB matter for solving this problem?

+

This relationship lets us express both diagonals in terms of one variable! Instead of having AC and DB as separate unknowns, we can write AC = 0.75 × DB, reducing our problem to one equation with one unknown.

How do I handle the 'X' in the area and the statement that DB = X?

+

The problem gives you two key facts: the area is 108X cm² and DB equals X cm. Substitute DB = X into your equation, then solve for the actual numerical value of X.

What if I get a different answer when I substitute back?

+

Double-check your algebra! Make sure you correctly converted 75% to 0.75, properly substituted DB = X, and divided 1080.375 \frac{108}{0.375} correctly. The calculation should give exactly 288.

Can I solve this problem using a different approach?

+

Yes! You could set up the equation as 12×34DB×DB=108X \frac{1}{2} \times \frac{3}{4}DB \times DB = 108X using fractions instead of decimals. Either way, you'll get 38DB2=108X \frac{3}{8}DB^2 = 108X and the same final answer.

🌟 Unlock Your Math Potential

Get unlimited access to all 18 Deltoid questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

More Questions

Click on any question to see the complete solution with step-by-step explanations