Question : In the given figure, PQR is a quadrant whose radius is 7 cm. A circle is inscribed in the quadrant as shown in the figure. What is the area (in cm2) of the circle?
Option 1: $385-221\sqrt{2}$
Option 2: $308-154\sqrt{2}$
Option 3: $154-77\sqrt{2}$
Option 4: $462-308\sqrt{2}$
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Correct Answer: $462-308\sqrt{2}$
Solution :
Let the radius of the circle = $r$ cm The radius of the quadrant = QM = QR = QP = 7 cm From the figure, $OS=OT=OM=QT=r$ cm ⇒ $OQ=(7-r)$ cm In $\triangle QTO$, $OQ^2=OT^2+QT^2$ ⇒ $(7-r)^2=r^2+r^2$ ⇒ $(7-r)^2=2r^2$ ⇒ $7-r=r\sqrt2$ ⇒ $r=\frac{7}{\sqrt2+1}=7(\sqrt2-1)$ The area of the circle = $\pi r^2$ ⇒ The area of the circle = $\pi [7(\sqrt2-1)]^2$ ⇒ The area of the circle = $\frac{22}{7} [7(\sqrt2-1)]^2$ ⇒ The area of the circle = $22×7×(3-2\sqrt2)=462-308\sqrt{2}$ cm2 Hence, the correct answer is $462-308\sqrt{2}$.
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Question : There is a wooden sphere of radius $6 \sqrt{3}$ cm. The surface area of the largest possible cube cut out from the sphere will be:
Option 1: $864$ cm2
Option 2: $464 \sqrt{3}$ cm2
Option 3: $462$ cm2
Option 4: $646\sqrt{3}$ cm2
Question : What is the perimeter of a square inscribed in a circle of radius 5 cm?
Option 1: $20 \sqrt{2}\ \mathrm{~cm}$
Option 2: $40\sqrt{2}\ \mathrm{~cm}$
Option 3: $30\sqrt{2}\ \mathrm{~cm}$
Option 4: $10\sqrt{2}\ \mathrm{~cm}$
Question : The base of a right prism is an equilateral triangle whose side is 10 cm. If the height of this prism is $10 \sqrt{3}$ cm, then what is the total surface area of the prism?
Option 1: $125 \sqrt{3}$ cm2
Option 2: $325 \sqrt{3}$ cm2
Option 3: $150 \sqrt{3}$ cm2
Option 4: $350 \sqrt{3}$ cm2
Question : The area of a sector of a circle is 308 cm2, with the central angle measuring 45°. The radius of the circle is:
Option 1: 14 cm
Option 2: 21 cm
Option 3: 7 cm
Option 4: 28 cm
Question : ABC is an equilateral triangle with a side of 12 cm. What is the length of the radius of the circle inscribed in it?
Option 1: $2 \sqrt{3}$ cm
Option 2: $8 \sqrt{3}$ cm
Option 3: $4 \sqrt{3} $ cm
Option 4: $6 \sqrt{3}$ cm
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