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A metal wire, when bent in the form of a...

A metal wire, when bent in the form of an equilateral triangle of largest area, encloses an area of `484sqrt(3) cm^(2)`. If the same wire is bent into the form of a circle of largest area, find the area of this circle.

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To solve the problem step by step, we will follow the reasoning laid out in the video transcript. ### Step 1: Understand the area of the equilateral triangle The area \( A \) of an equilateral triangle with side length \( x \) is given by the formula: \[ A = \frac{\sqrt{3}}{4} x^2 \] We know from the problem that the area of the triangle is \( 484 \sqrt{3} \, \text{cm}^2 \). ### Step 2: Set up the equation We can set up the equation using the area formula: \[ \frac{\sqrt{3}}{4} x^2 = 484 \sqrt{3} \] ### Step 3: Solve for \( x^2 \) To eliminate \( \sqrt{3} \) from both sides, we divide both sides by \( \sqrt{3} \): \[ \frac{1}{4} x^2 = 484 \] Now, multiply both sides by 4: \[ x^2 = 484 \times 4 \] Calculating \( 484 \times 4 \): \[ x^2 = 1936 \] ### Step 4: Find \( x \) Now, take the square root of both sides to find \( x \): \[ x = \sqrt{1936} = 44 \, \text{cm} \] ### Step 5: Calculate the perimeter of the equilateral triangle The perimeter \( P \) of an equilateral triangle is given by: \[ P = 3x \] Substituting the value of \( x \): \[ P = 3 \times 44 = 132 \, \text{cm} \] ### Step 6: Relate the perimeter to the circle When the wire is bent into the shape of a circle, the circumference \( C \) of the circle is equal to the perimeter of the triangle: \[ C = 132 \, \text{cm} \] The circumference of a circle is given by: \[ C = 2\pi r \] Setting the two expressions for circumference equal gives: \[ 2\pi r = 132 \] ### Step 7: Solve for \( r \) To find the radius \( r \), we can rearrange the equation: \[ r = \frac{132}{2\pi} \] Substituting \( \pi \) with \( \frac{22}{7} \): \[ r = \frac{132}{2 \times \frac{22}{7}} = \frac{132 \times 7}{44} = \frac{924}{44} = 21 \, \text{cm} \] ### Step 8: Calculate the area of the circle The area \( A \) of a circle is given by: \[ A = \pi r^2 \] Substituting the value of \( r \): \[ A = \pi \times (21)^2 = \pi \times 441 \] Using \( \pi \approx \frac{22}{7} \): \[ A = \frac{22}{7} \times 441 \] Calculating: \[ A = \frac{22 \times 441}{7} = \frac{9702}{7} = 1386 \, \text{cm}^2 \] ### Final Answer The area of the circle is: \[ \boxed{1386 \, \text{cm}^2} \] ---
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ICSE-AREA AND PERIMETER OF PLANE FIGURES-EXERCISE 20(C)
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