Question 1.

In each example given below, radius of base of a cylinder and its height are given. Then find the curved surface area and total surface area.

i. r = 7 cm, h = 10 cm

ii. r = 1.4 cm, h = 2.1 cm

iii. r = 2.5 cm, h = 7 cm

iv. r = 70 cm, h = 1.4 cm

v. r = 4.2 cm, h = 14 cm

= 78.57 sq.cm

∴The radius of the cylinder is 5 cm and the area of its base is 78.57 sq.cm.

ii. Area of sheet required to made a lid = Curved surface area of lid + Area of upper surface

= 2πrh_{2} + πr²

= πr (2h_{2} + r)

= x 14 x (2 x 2 + 14)

= 22 x 2 x (4 + 14)

= 22 x 2 x 18

= 792 sq cm

∴ The area of the sheet required to make the cylindrical container is 2376 sq. cm and the approximate area of a sheet required to make the lid is 792 sq. cm.