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# Volume & Surface Areas

1.

The number of coins of radius 0.75 cm and thickness 0.2 cm to be melted to make a right circular cylinder of height 8 cm and base radius 3 cm is

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2.

A cylindrical pencil sharpened at one edge is the combination of

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3.

Ramesh has a metal cube. He paints all sides of the cube with green color. He divides the cube into smaller cubes of volume 1 cu.m. each. How many of these smaller cubes will not have green color on even one of its sides if the volume of larger cube is 27 cu.m.?

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4.

If a rectangular cuboid is 9cm long and 8cm wide with volume of 450cm⊃3; then height of cuboid in 'cm' is

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5.

A cube whose edge is 20 cm long, has circles on each of its faces painted black. What is the total area of the unpainted surface of the cube if the circles are of the largest possible areas?

Diameter of largest circle = 20 cm.
∴ Area of circle = 100π cm⊃2;
∴ Area of 6 circles = 6 × 100π = 600π cm⊃2; (∵ there are six faces in a cube)
Also, Area of cube = 6 × (20)⊃2; = 2400 cm⊃2;
Area of unpainted surface = 2400 – 600π
= 2400 – 600 × 22/7
= 514.28 cm⊃2;.

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6.

Two right circular cones of equal curved surface areas have slant heights in the ratio of 3 : 5. Find the ratio of their radii.

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7.

Surface area of sphere is

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8.

The total surface area of a hemispherical solid having radius 7 cm is

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9.

If the radius of cylinder is halved and height is doubled, then what will be the curved surface area?

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10.

What will be total cost of polishing curved surface of a wooden cylinder at rate of Rs. 20 per sq.m, if it has 40 cm diameter and 7m height?