Question

30 circular plates, each of radius 14 cm and thickness 3 cm are placed one above the another to form a cylindrical solid.

Find

1. the total surface area.
2. volume of the cylinder so formed.

Answer 1

Given, radius of a circular plate, r = 14 cm

Thickness of a circular plate = 3 cm

Thickness of 30 circular plates = 30 x 3 = 90 cm

Since, 30 circular plates are placed one above the another to form a cylindrical solid. Then, Height of the cylindrical solid, h = Thickness of 30 circular plates = 90 cm

1. Total surface area of the cylindrical solid so formed

= 2πr(h+ r)

= 2 x (22/7) x 14(90+ 14)

= 44 x 2 x 104 

= 9152 cm²

Hence, the total surface area of the cylindrical solid is 9152 cm²,

2. Volume of the cylinder so formed = πr²h

= (22/7) (14)² x 90 

= (22/7) x 14 x 14 x 90

= 22 x 28 x 90 

= 55440 cm³

Hence, the volume of the cylinder so formed is 55440 cm³.