Examples

Chapter 11 Class 8 Mensuration
Serial order wise

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Example 11 A rectangular piece of paper 11 cm × 4 cm is folded without overlapping to make a cylinder of height 4 cm. Find the volume of the cylinder. Also, Length of rectangle = 11 cm Breadth of rectangle = 4 cm Since rectangle is rolled along its width to make cylinder Height of cylinder = Width of rectangle = 4 cm Let r be the radius of the cylinder. Now, since rectangle is rolled to become cylinder ∴ Perimeter of bottom of the cylinder = Length of the rectangle Circumference of circle = 11 2πr = 11 2×22/7×𝑟 = 11 44/7×𝑟 = 11 𝑟 = 11 × 7/44 𝑟 = 7/4 Now, Volume of cylinder = 𝜋𝑟^2 ℎ = 22/7×(7/4)^2×4 = 22/7×7/4×7/4×4 = (22 × 7)/4 = 154/4 = 77/2 = 38.5 cm3

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.