Exercise 20A

Find the minimum length in cm and correct to nearest whole number of the thin metal sheet required to make a hollow and closed cylindrical box of diameter 20 cm and height 35 cm. Given that the width of the metal sheet is 1 m. Also, find the cost of the sheet at the rate of Rs. 56 per m. Find the area of metal sheet required, if 10% of it is wasted in cutting, overlapping, etc.

Height of the cylinder box = h = 35 cm Base radius of the cylinder box = r = 10 cm Width of metal sheet = 1m = 100 cm Area of metal sheet required = total surface area of the box Length x width =...

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A cylindrical container with diameter of base 42 cm contains sufficient water to submerge a rectangular solid of iron with dimensions 22 cm x 14 cm x 10.5 cm. Find the rise in level of the water when the solid is submerged.

Diameter of cylindrical container = 42 cm it’s radius (r) = 21 cm Dimensions of rectangular solid = 22cm x 14cm x 10.5cm The volume of solid = 22 x 14 x 10.5 cm3 ….. (i) Let the height of water = h...

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A cylinder has a diameter of 20 cm. The area of curved surface is 100 sq cm. Find: (i) the height of the cylinder correct to one decimal place. (ii) the volume of the cylinder correct to one decimal place.

The diameter of the cylinder = 20 cm the radius (r) = 10 cm and the curved surface area = 100 cm2 Height = h cm (i) Curved surface area \[\begin{array}{*{35}{l}} =\text{ }2\pi rh  \\ 2\pi rh\text{...

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A cylinder of circumference 8 cm and length 21 cm rolls without sliding for 4½ seconds at the rate of 9 complete rounds per second. Find: (i) distance travelled by the cylinder in 4½ seconds, and (ii) the area covered by the cylinder in 4½ seconds

Base circumference of cylinder (c) = 8 cm So, the radius \[=\text{ }c/2\pi \text{ }=\text{ }\left( 8\text{ x }7 \right)/\text{ }\left( 2\text{ x }22 \right)\text{ }=\text{ }14/11\text{ }cm\] Length...

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