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 are r 4.2 h 7
Answers
Answer:
Given: r = 7 cm and h = 10 cm To find: Curved surface area of cylinder and total surface area Curved surface area of the cylinder = 2πrh = 2 x (22/7) x 7 x 10 = 2 x 22 x 10 = 440 sq.cm Total surface area of the cylinder: = 2πr(h + r) = 2 x (22/7) x 7(10 + 7) = 2 x (22/7) x 7 x 17 = 2 x 22 x 17 = 748 sq.cm The curved surface area of the cylinder is 440 sq.cm and its total surface area is 748 sq.cm ii. Given: r = 1.4 cm and h = 2.1 cm To find: Curved surface area of cylinder and total surface area Curved surface area of the cylinder = 2πrh = 2 x (22/7) x 1.4 x 2.1 = 2 x 22 x 0.2 x 2.1 = 18.48 sq.cm Total surface area of the cylinder = 2πr (h + r) = 2 x (22/7) x 1.4 (2.1 + 1.4) = 2 x (22/7) x 1.4 x 3.5 = 2 x 22 x 0.2 x 3.5 = 30.80 sq.cm ∴ The curved surface area of the cylinder is 18.48 sq.cm and its total surface area is 30.80 sq.cm. iii. Given: r = 2.5 cm and h = 7 cm To find: Curved surface area of cylinder and total surface area Curved surface area of the cylinder = 2πrh = 2 x (22/7) x 2.5 x 7 = 2 x 22 x 2.5 = 110 sq.cm Total surface area of the cylinder = 2πr(h + r) = 2 x (22/7) x 2.5 (7+ 2.5) = 2 x (22/7) x 2.5 x 9.5 = 1045/7 = 149.29 sq.cm ∴ The curved surface area of the cylinder is 110 sq.cm and its total surface area is 149.29 sq.cm. iv. Given: r = 70 cm and h = 1.4 cm To find: Curved surface area of cylinder and total surface area Curved surface area of the cylinder = 2πrh = 2 x (22/7) x 70 x 1.4 = 2 x 22 x 10 x 1.4 = 616 sq.cm Total surface area of the cylinder = 2πr(h + r) = 2 x (22/7) x 70(1.4 + 70) = 2 x (22/7) x 70 x 71.4 = 2 x 22 x 10 x 71.4 = 2 x 22 x 714 = 31416 sq.cm ∴ The curved surface area of the cylinder is 616 sq.cm and its total surface area is 31416 sq.cm. v. Given: r = 4.2 cm and h = 14 cm To find: Curved surface area of cylinder and total surface area Curved surface area of the cylinder = 2πrh = 2 x (22/7) x 4.2 x 14 = 2 x 22 x 4.2 x 2 = 369.60 sq.cm Total surface area of the cylinder = 2πr (h + r) = 2 x (22/7) x 4.2 (14+ 4.2) = 2 x (22/7) x 4.2 x 18.2 = 2 x 22 x 0.6 x 18.2 = 480.48 sq.cm ∴ The curved surface area of the cylinder is 369.60 sq.cm and its total surface area is 480.48 sq.cm.