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# Short Answer Type Questions- Areas Related to Circles Class 10 Notes | EduRev

## Class 10 : Short Answer Type Questions- Areas Related to Circles Class 10 Notes | EduRev

The document Short Answer Type Questions- Areas Related to Circles Class 10 Notes | EduRev is a part of the Class 10 Course Mathematics (Maths) Class 10.
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Q1. In a circular table cover of radius 70 cm, a design is formed leaving an equilateral triangle ABC in the middle as shown in the figure. Find the total area of the design.

Sol. âˆµ Radius of the circle = 70 cm and O is the centre of the circle.
âˆ´ OA = OB = OC
Since âˆ†ABC is an equilateral triangle,
âˆ´âˆ ABO = âˆ BOC= âˆ CDA = 120Â°
Draw ODâŠ¥BC
Now in right Î”BDO,

âˆ´ Area of equilateral Î”ABC =

Also, area of the circle = Ï€r2

= 22 Ã— 10 Ã— 70 cm2 = 15400 cm2

âˆ´ Area of the shaded region
= 15400 cm2 âˆ’ (3675âˆš3) cm
= 15400 cm2 âˆ’ (3675 Ã— 1.73) cm2
= 15400 cm2 âˆ’ 6357.75 cm2 = 9042.25 cm2.

Q2. Calculate the area other than the area common between two quadrants of the circles of radius 16 cm each, which is shown as the shaded region in the figure.

Sol.

âˆ´ Area of the shaded region-I =

Similarly, in area of the shaded region-II 384/7 cm2

âˆ´ Total area of the shaded region = [Area of shaded region-I] + [Area of shaded region-II]

Q3. In the figure, PQ = 24 cm, PR = 7 cm and O is the centre of the circle. Find the area of shaded region. (Take Ï€ = 3.14)

Sol. In right Î” RPQ,
PR2 + PQ2 = RQ2
â‡’ 72 + 242 = RQ2
â‡’ 49 + 576 = RQ2
â‡’ 625 = RQ2

â‡’ Radius of semi-circle = 25/2 cm

âˆ´ Area of semi-circle RQP

âˆ´ Area of the shaded region=Area of semi-circle RQP âˆ’ ar (right Î” RPQ)
=245.31 cm2 = 84 cm2 = 161.31 cm2.

Q4. The area of an equilateral triangle is 49âˆš3. Taking each angular point as centre, circles are drawn with radius equal to half length of the side of the triangle. Find the area of triangle not included in the circles. [Take âˆš3 = 1.73]

Sol. Let the given equilateral triangle be ABC, such that its side = 14 cm.

Since each angle of an equilateral triangle = 60Â°,
âˆ´ Area of a sector having Î¸ as 60Â° and radius 14/2 i.e. 7 cm.

â‡’ Area of 3 sectors

= 77 cm2
âˆ´ Area of the shaded region = [Area of equilateral âˆ† ABC] âˆ’ [Area of 3 sectors]
= 84.77 cm2 âˆ’ 77 cm2 = 7.77 cm2.

Q5. Four equal circles are described at the four corners of the square so that each touches two of the others, the shaded area enclosed between the circles is 22/7 cm2 Find the radius of each circle.

Sol. Let 'r' cm be the radius of each circle.
âˆ´ side of the square = 2r

But the area of shaded region

But r cannot be âˆ’ ve, so r = 2 cm

Q6. A square OABC is inscribed in a quadrant OABQ of a circle as shown in the figure. If OA = 14 cm, find the area of the shaded region. [use Ï€ = 22/7]

Sol. OABC is a square with side = 14 cm.
âˆ´ Area of the square OABC = 14 cm Ã— 14 cm = 196 cm2

Now, the diagonal of the square OABC

âˆ´ Area of the quadrant OABQ

âˆ´ Area of the shaded region
= 308 cm2 âˆ’ 196 cm2 = 112 cm2.

Q7. In the figure, ABDC is a quadrant of a circle of radius 14 cm and a semi-circle is drawn with diameter BC. Find the area of the shaded region.

Sol. We have, in the right Î” ABC,

BC2 = AB2 + AC2 = 142 + 142 = 2 (14)2

âˆ´ Radius of the semi-circle =

âˆ´ Area of semi-circle BEC

= 98 cm2

= 154 cm2 + 98 cm2 âˆ’ 154 cm2 = 98 cm2.

Q8. In the figure, find the perimeter of the shaded region where, ADC, AEB and BFC are semicircles on diameters AC, AB and BC respectively.

= 2.1 cm

Diameter of semi-circle AEB = 2.8 cm

âˆ´ Circumference of semi-circle

Diameter of semi-circle BFC = 1.4 cm
â‡’ Radius of semi-circle BFC = 0.7 cm
âˆ´ Circumference of semi-circle BFC

âˆ´ Total perimeter of the shaded region = 6.6 cm + 4.4 cm + 2.2 cm = 13.2 cm.

Q9. In the figure, arcs are drawn by taking vertices A, B and C of an equilateral triangle of side 10 cm to intersect the sides BC, CA and AB at their respective mid-points D, E and F. Find the area of the shaded region.

[use Ï€ = 3.14]

Sol. âˆµ Î”ABC is an equilateral triangle.
âˆ´âˆ A = âˆ B = âˆ C = 60Â°
Area of sector AFEA

Area of all the three sectors

Thus, area of the shaded region = 39.25 cm2.

Q10. In figure OABC is a quadrant of a circle of radius 7 cm. If OD = 4 cm, find the area of the shaded region. [Use Ï€ = 22/7]

Sol. We have, the centre of the circle as â€˜Oâ€™ and radius (r) = 7 cm

=  7 Ã— 2 = 14 cm2
âˆ´ Area of the shaded region = (Area of the quadrant OABC) â€“ (Area of âˆ†COD)

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## Mathematics (Maths) Class 10

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