3. A room 8 m long 6 m board and 3 m high has two windows 2 1 1 m × 1 m and a door 2 m × 2 1 1 m. Find the cost of papering the walls will paper 50 cm wide at Rs. 40 per metre.
4. 50 circular plates, each of radius 7 cm and thickness 2 1 cm, are placed one above the other to form a solid right circular cylinder. Find the total surface area.
5. A tent in the shape of a right circular cylinder surmounted by a right circular cone. The heights of the cylindrical and the conical parts are 40 m and 21 m respectively. If the base diameter of the tent is 56 m, find the area of the required canvas to make this tent if 20% of the area is consumed in folding and sewing.
6. A toy is in the form of a right circular cylinder closed at one end and with a hemisphere on the other end. The height and the radius of the base are 15 cm and 6 cm respectively. The radius of the hemisphere are cylinder are same. Calculate the total surface area and the volume of the toy. if the toy is painted at the rate of Rs. 2.50 per 10 cm2 , find the cost of painting the toy.
7. An iron pillar has some portion in the form of a right circular cylinder an remaining in the form of a right circular cone. The radius of the base of each of the cone and the cylinder is 8 cm. The cylindrical portion is 240 cm high and the conical part is 36 cm high. Find the weight of the pillar, if one cubic cm of iron weights 7.8 g.
8. A solid metallic sphere of diameter 28 is melted and recasted into a number of smaller cones, each of diameter 3 2 4 cm and height 3 cm. Find the number of cones so formed.
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Answer:
Step-by-step explanation:
length = 8m
breadth = 6m
height = 3m
2 doors = 2m x 1m x 2 = 4m^2
2 windows = 1.5m x 1m x 2 = 3m^2
curved surface area of room = 2(l+b)h
= 2(8+6)3
= 2 x 14 x 3
= 84 m^2
Area to be painted = 84m^2 - (4m^2 + 3m^2)
= 77m^2
cost of painting = 77m^2 x 3.80
= Rs 292.6
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