Rectangle Side Ratio Problem: Finding Length m Using sqrt(x/2)

Rectangle Diagonals with Radical Ratios

The rectangle ABCD is shown below.

AB = X

The ratio between AB and BC is x2 \sqrt{\frac{x}{2}} .


The length of diagonal AC is labelled m.

XXXmmmAAABBBCCCDDD

Determine the value of m:

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Select the correct statement
00:03 Mark the side with X according to the given data
00:07 Insert this value into the given ratio and solve for BC
00:17 Multiply by the reciprocal
00:22 Isolate BC
00:30 Divide X by twice the factor of square root X
00:34 Simplify wherever possible
00:39 This is the length of side BC
00:50 Apply the Pythagorean theorem in triangle ABC
00:57 Insert into the formula appropriate values and solve as follows
01:16 Add 1 to match our statement
01:33 Use the distributive law
01:36 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

The rectangle ABCD is shown below.

AB = X

The ratio between AB and BC is x2 \sqrt{\frac{x}{2}} .


The length of diagonal AC is labelled m.

XXXmmmAAABBBCCCDDD

Determine the value of m:

2

Step-by-step solution

We know that:

ABBC=x2 \frac{AB}{BC}=\sqrt{\frac{x}{2}}

We also know that AB equals X.

First, we will substitute the given data into the formula accordingly:

xBC=x2 \frac{x}{BC}=\frac{\sqrt{x}}{\sqrt{2}}

x2=BCx x\sqrt{2}=BC\sqrt{x}

x2x=BC \frac{x\sqrt{2}}{\sqrt{x}}=BC

x×x×2x=BC \frac{\sqrt{x}\times\sqrt{x}\times\sqrt{2}}{\sqrt{x}}=BC

x×2=BC \sqrt{x}\times\sqrt{2}=BC

Now let's look at triangle ABC and use the Pythagorean theorem:

AB2+BC2=AC2 AB^2+BC^2=AC^2

We substitute in our known values:

x2+(x×2)2=m2 x^2+(\sqrt{x}\times\sqrt{2})^2=m^2

x2+x×2=m2 x^2+x\times2=m^2

Finally, we will add 1 to both sides:

x2+2x+1=m2+1 x^2+2x+1=m^2+1

(x+1)2=m2+1 (x+1)^2=m^2+1

3

Final Answer

m2+1=(x+1)2 m^2+1=(x+1)^2

Key Points to Remember

Essential concepts to master this topic
  • Ratio Rule: Convert ABBC=x2 \frac{AB}{BC} = \sqrt{\frac{x}{2}} to find BC length
  • Technique: Use cross-multiplication: BC=x2x=2x BC = \frac{x\sqrt{2}}{\sqrt{x}} = \sqrt{2x}
  • Check: Verify with Pythagorean theorem: x2+2x=m2 x^2 + 2x = m^2

Common Mistakes

Avoid these frequent errors
  • Incorrectly simplifying the radical ratio
    Don't leave BC=x2x BC = \frac{x\sqrt{2}}{\sqrt{x}} unsimplified = wrong diagonal calculation! This creates messy expressions that lead to algebraic errors. Always simplify radicals: x2x=x×2=2x \frac{x\sqrt{2}}{\sqrt{x}} = \sqrt{x} \times \sqrt{2} = \sqrt{2x} .

Practice Quiz

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What is the ratio between the orange and gray parts in the drawing?

FAQ

Everything you need to know about this question

How do I handle the square root in the ratio?

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Break down x2 \sqrt{\frac{x}{2}} into x2 \frac{\sqrt{x}}{\sqrt{2}} . This makes cross-multiplication easier: xBC=x2 \frac{x}{BC} = \frac{\sqrt{x}}{\sqrt{2}} , so BC=x2x BC = \frac{x\sqrt{2}}{\sqrt{x}} .

Why do we add 1 to both sides at the end?

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The problem asks us to match one of the given answer choices. By adding 1 to both sides of x2+2x=m2 x^2 + 2x = m^2 , we get (x+1)2=m2+1 (x+1)^2 = m^2 + 1 , which matches option D.

Can I use the Pythagorean theorem directly?

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Yes! Since ABCD is a rectangle, triangle ABC is a right triangle. Use AB2+BC2=AC2 AB^2 + BC^2 = AC^2 where AC is the diagonal m.

What if I get confused by all the square roots?

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Take it step by step. First find BC using the ratio, then substitute both AB and BC into the Pythagorean theorem. Simplify radicals early to avoid confusion later!

How do I know which diagonal to use?

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The problem specifically states that AC is labeled m. In a rectangle, both diagonals are equal, so it doesn't matter which one you calculate - they'll give the same answer.

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