Surface Area of a Cylinder | Mensuration | Assessment | English | Grade 8

Lateral surface area of a cylinder = ________________.

• 2πr/h

• 2πr + h

• 2πrh

• πrh

Total surface area of a cylinder with radius = 7 cm and height 15 cm is ______

• 44 cm²

• 660 cm²

• 968 cm²

• 2310 cm²

Answer explanation

Total surface area of cylinder = 2πr(r+h) = 2 × (22/7) × 7 × (7 + 15) = 2 × 22 × 22 = 968 cm²

Lateral surface area of a cylinder with radius = 14 cm and height = 32 cm is ______.

• 2816 cm²

• 4048 cm²

• 19712 cm²

• 2829 cm²

Answer explanation

Lateral surface area of cylinder = 2πrh = 2 × (22/7) × 14 × 32 = 2816 cm²

If the height of a cylinder becomes 1/4 of the original height, then which of the following will be true?

• Curved surface area of the cylinder will be doubled.

• Curved surface area of the cylinder will remain unchanged

• Curved surface area of the cylinder will be halved.

• Curved surface area will be 1/4 of the original curved surface.

Answer explanation

Curved (lateral) surface area of a cylinder = 2πrh If the height becomes 1/4 of the original height, then the curved surface area = 2πr(h/4) = ¼ 2πrh i.e., Curved surface area will be 1/4 of the original curved surface. So, option 4 is correct.

A road roller takes 540 complete revolutions to move once over to level a road. If the diameter of the road roller is 70 cm and the length is 1.5 m, then what is the area if the road?

• 3.3 m²

• 1782 m²

• 1786 m²

• 2198 m²

Answer explanation

1 m = 100 cm so, 70 cm = 0.7 m = diameter Hence radius = r = 0.7/2 = 0.35 m Lateral surface area of cylinder (road roller) = 2πrh = 2 × (22/7) × 0.35 × 1.5 = 3.3 m² Area of road covered by road roller in 1 revolution = 3.3 m² Area of the road = Area of road covered in 1 revolution x total number of revolution = 3.3 m² × 540 = 1782 m²

The lateral surface area of a hollow cylinder is 5544 cm². It is cut along its height and a rectangular sheet of width 66 cm is formed. What is the perimeter of the rectangular sheet?

• 5544 cm

• 264 cm

• 150 cm

• 300 cm

Answer explanation

Lateral surface area of cylinder = 2πrh According to the question, we have, Lateral surface area of cylinder = area of rectangular sheet i.e. 5544 cm² = length x width 5544 cm²= length x 66 cm length = 5544 cm²/ 66 cm = 84 cm Perimeter of rectangular sheet = 2(length + breadth) = 2(84 + 66) = 2(150) = 300 cm So, option 4 is correct.

A closed cylindrical tank of radius 28 m and height 5 m is made from a sheet of metal. How much sheet of metal is required?

• 5810 m²

• 5812 m²

• 5815 m²

• 5808 m²

Answer explanation

Total surface area of cylinder = 2πr(r + h) = 2 × (22/7) × 28 × (28 + 5) = 2 × 22 × 4 × 33 = 5808 m²