### Exercise 12.1

**(Unless stated otherwise, use pi =22/7**

**Question 1. The radii of two circles are 19 cm and 9 cm respectively. Find the radius of the circle which has circumference equal to the sum of the circumferences of the two circles.**

**Question 2. The radii of two circles are 8 cm and 6 cm respectively. Find the radius of the circle having area equal to the sum of the areas of the two circles.**

**Question 3. Figure depicts an archery target marked with its five scoring regions from the centre outwards as Gold, Red, Blue, Black and White. The diameter of the region representing Gold score is 21 cm and each of the other bands is 10.5 cm wide. Find the area of each of the five scoring regions.**

**Question 4. The wheels of a car are of diameter 80 cm each. How many complete revolutions does each wheel make in 10 minutes when the car is travelling at a speed of 66 km per hour?**

**Question 5. Tick the correct answer in the following and justify your choice. If the perimeter and the area of a circle are numerically equal, then the radius of the circle is**

Exercise 12.2

**Question 1. Find the area of a sector of a circle with a radius 6 cm if angle of sector is 60°**

**Question 2. Find the area of a quadrant of a circle whose circumference is 22 cm. (Unless stated otherwise, use pi= 22/7 )**

**Question 3. The length of the minute hand of a clock is 14 cm. Find the area swept by the minute hand in 5 minutes.**

**Question 4. A chord of a circle of radius 10 cm subtends a right angle at the centre. Find the area of the corresponding:(Use pi = 3.14)**

**Question 5. In a circle of radius 21 cm, an arc subtends an angle of 60° at the centre.Find:(I) the length of the arc(ii) area of the sector formed by the arc(iii) area of the segment formed by the corresponding chord**

**Question 6. A chord of circle of radius 15 cm subtends an angle of 60° at the centre. Find the areas of the corresponding minor and major segments of the circle.**

**Question7. A chord of a circle of radius 12 cm subtends an angle of 120° at the centre. Find the area of the corresponding segment of the circle.(Use 1t = 3.14 and root 3 = 1.73)**

Question 8. A horse is tied to a peg at one corner of a square-shaped grass field of side 15 m by means of a 5 m long rope (see figure). Find

**(I) the area of that part of the field in which the horse can graze.(ii) the increase in the grazing area if the rope were 10 m long instead of 5 m. (Use pi = 3.14)**

Question 9. A brooch is made with silver wire in the form of a circle with a diameter 35 mm. The wire is also used in making 5 diameters which divide the circle into 10 equal sectors as shown in the figure. Find :

**(I) the total length of the silver wire required.(ii) the area of each sector of the brooch.**

**Question 10. An umbrella has 8 ribs which are equally spaced (see Fig.). Assuming umbrella to be a flat circle of radius 45 cm, find the area between the two consecutive ribs of the umbrella.**

**Question 11. A car has two wipers which do not overlap. Each wiper has a blade of length 25 cm sweeping through an angle of 115°. Find the total area cleaned at each sweep of the blades.**

**Question 12. To warn ships for underwater rocks, a lighthouse spreads a red coloured light over a sector of angle 80° to a distance of 16.5 km. Find the area of the sea over which the ships are warned.(Use pi = 3.14)**

**Question 13. A round table cover has six equal designs as shown in the figure. If the radius of the cover is 28 cm, find the cost of making the designs at the rate of 0.35 per cm2. (Use pi = 3.14)**

**Question 14. Tick the correct answer in the following :The area of a sector of angle p (in degrees) of a circle with radius R is**

#### Exercise 12.3

**(Unless stated otherwise, use pi= 22/7Question 1. Find the area of the shaded region in the figure, if PQ = 24 cm, PR = 7 cm and O is the centre of the circle**

**Question 2. Find the area of the shaded region in the figure, if the radii of the two concentric circles with centre O are 7 cm and 14 cm respectively and LAOC = 40°.**

**Question 3. Find the area of the shaded region in the figure, if ABCD is a square of side 14 cm and APD and BPC are semicircles.**

**Question 4. Find the area of the shaded region in the given figure where a circular arc of radius 6 cm has been drawn with vertex O of an equilateral triangle OAB of side 12 cm as the centre.**

**Question 5. From each corner of a square of side 4 cm, a quadrant of a circle of radius 1 cm is cut and also a circle of diameter 2 cm is cut as shown in the figure. Find the area of the remaining portion of the square.**

**Question 6. In a circular table covered of radius 32 cm, a design is formed leaving an equilateral triangle ABC in the middle as shown in the figure. Find the area of the design.**

**Question 7. In the figure, ABCD is a square of side 14 cm. With centres A, B, C and D, four circles are drawn such that each circle touch externally two of the remaining three circles. Find the area of the shaded region.**

**Question 8. Figure depicts a racing track whose left and right ends are semicircular.**

**The distance between the two inner parallel line segments is 60 m and they are each 106 m long. If the track is 10 m wide, find :(I) the distance around the track along its inner edge(ii) the area of the track**

**Question 9. In the figure, AB and CD are two diameters of a circle (with centre 0) perpendicular to each other and OD is the diameter of the smaller circle. If OA = 7 cm, find the area of the shaded region.**

**Question 10. The area of an equilateral triangle ABC is 17320.5 cm2. With each vertex of the triangle as the centre, a circle is drawn with a radius equal to half the length of the side of the triangle (see figure). Find the area of the shaded region.**

**Question 11. On a square handkerchief, nine circular designs each of radius 7 cm are made (see Fig.). Find the area of the remaining portion of the handkerchief.**

**Question 12. In Fig. OACB is a quadrant of a circle with centre O and radius 3.5 cm. If OD = 2 cm, find the area of the**

**Question 13. In figure, a square OABC is inscribed in a quadrant OPBQ. If OA = 20 cm, find the area of the shaded region. (Use pi = 3.14)**

**Question 14. AB and CD are respectively arcs of two concentric circles of radii 21 cm and 7 cm and centre O (see figure). If LAOB = 30°, find the area of the shaded region.**

**Question 15. In figure, ABC is a quadrant of circle of radius 14 cm and a semicircle is drawn with BC as diameter. Find the area of the shaded region.**

**Question 16. Find the area of the shaded region between the two quadrants of circles of radius 8 cm each shown in the given figure:**

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