When a particular wire is bent into the shape of a square, then the area of the square turns out to be 81 cm2. When the same wire is bent into a circle, then the radius of the circle (correct to two decimal places) is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 5.73
Bending does not change the length of the wire, so the perimeter of the square equals the circumference of the circle.
The length of the wire (from the square of area 81 cm2):
Side \(=\sqrt{81}=9\) cm
Perimeter \(=4\times9=36\) cm
The radius (the circumference is the same 36 cm):
\(2\pi r=36\)
\(\displaystyle r=\frac{36}{2\pi}=\frac{36\times7}{2\times22}=\frac{63}{11}\approx5.73\) cm