Volume and Surface Area of Solid Figures
- The floor of a rectangular hall has a perimeter 250 m. If the cost of painting the four walls at the rate of ₹ 10 per sq m is ₹15000, then find the height of the hall ?
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Area of 4 wails = Lateral surface area perimeter = 2(l + b) = 250
⇒ l + b = 250/2 = 125 m
Area to be painted = Cost/Rate = 15000/10 = 1500 sq m
Area of 4 wails = 2(l + b)h = 250 hCorrect Option: B
Area of 4 wails = Lateral surface area perimeter = 2(l + b) = 250
⇒ l + b = 250/2 = 125 m
Area to be painted = Cost/Rate = 15000/10 = 1500 sq m
Area of 4 wails = 2(l + b)h = 250 h
⇒ 250h = 1500
∴ h = 1500/250 = 6 m
- The diameter of a roller is 84 cm and its length 120 cm. Its takes 500 complete revolutions to move once over to level a playground (in sq m) ?
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In one revolution, area covered = Covered surface area
⇒ 2πrh = 2 x (22/7) x 42 x 120 = 31680 sq cm
in 500 revolutions,
Area covered = 31680 x 500Correct Option: D
In one revolution, area covered = Covered surface area
⇒ 2πrh = 2 x (22/7) x 42 x 120 = 31680 sq cm
in 500 revolutions,
Area covered = 31680 x 500 = (1584 x 104) sq cm
= (1584 x 104) / (104) = 1584 sq m
- A cylindrical pillar is 50 cm in diameter and 3.5 m in height. Find the cost of painting the covered surface of the pillar at the rate ₹ 10 per sq m . ?
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Curved surface area = 2πrh
= 2 x (22/7) x 0.25 x 3.5Correct Option: D
Curved surface area = 2πrh
= 2 x (22/7) x 0.25 x 3.5
= 5.5 sq m
∴ Cost of painting 5.5 sq m = 10 x 5.5
= ₹ 55
- A pillar 14 cm in diameters is 5 m high. How much material was used to construct it ?
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Volume of the cylinder = πr2h
Correct Option: D
Volume of the cylinder = πr2h
= (22/7) x 7 x 7 x 500 = 77000
= (77 x 103) cm3
- The curved surface area of a right circular cone of radius 14 cm is 440 sq cm. what is the slant height of the cone ?
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Curved surface area of right circular cone = πrl
∴ 440 = (22/7) x 14 x lCorrect Option: A
Curved surface area of right circular cone = πrl
∴ 440 = (22/7) x 14 x l
⇒ l = (440 x 7) / (22 x 14) = 10 cm