Advertisements
Advertisements
Question
The surface area of a sphere is same as the curved surface area of a right circular cylinder whose height and diameter are 12 cm each. The radius of the sphere is
Options
3 cm
4 cm
6 cm
12 cm
Solution
Let r be the radius of sphere
But,
Surface area of sphere = C.S.A. of cylinder
`4pir^2 = 2pirh`
`4r^2 = 2 xx 6 xx 12 `
`r^2 = (2 xx 6 xx 12)/4`
`r = 6cm`
APPEARS IN
RELATED QUESTIONS
A solid is composed of a cylinder with hemispherical ends. If the whole length of the solid is 104 cm and the radius of each of the hemispherical ends is 7 cm, find the cost of polishing its surface at the rate of Rs 10 per dm2 .
A wooden toy was made by scooping out a hemisphere of same radius from each end of a solid cylinder. If the height of the cylinder is 10 cm, and its base is of radius 3.5 cm, find the volume of wood in the toy. `[\text{Use}pi 22/7]`
A metal parallelopiped of measures 16 cm x 11 cm x 10 cm was melted to make coins. How many coins were made if the thickness and diameter of each coin were 2 mm and 2 cm respectively?
Radius of a sphere is 14 cm. Find the surface area of the sphere.
A canal is 300 cm wide and 120 cm deep. The water in the canal is flowing with a speed of 20 km/hr. How much area will it irrigate in 20 minutes if 8 cm of standing water is desired ?
The dimensions of a metallic cuboid are 100cm× 80 cm× 64cm. It is melted and recast into a cube. Find the surface area of the cube.
Two cubes, each of volume 64 cm3, are joined end to end. Find the total surface area of the resulting cuboid.
The slant height of the frustum of a cone is 4 cm and the perimeters (i.e. circumferences) of its circular ends are 18 cm and 6 cm. Find the curved surface area of the frustum.
A farmer connects a pipe of internal diameter 20 cm from a canal into a cylindrical tank which is 10 m in diameter and 2 m deep. If the water flows through the pipe at the rate of 4 km/hr, then in how much time will the tank be filled completely?
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?
