Area Of Cone

Chapter 11 Class 9 Surface Areas and Volumes
Concept wise

### Transcript

Ex 11.1, 5 What length of tarpaulin 3 m wide will be required to make conical tent of height 8 m and base radius 6 m? Assume that the extra length of material that will be required for stitching margins and wastage in cutting is approximately 20 cm (Use π = 3.14). Tarpaulin will be on the curved surface area of tent Lets find curved surface area first Curved surface area of tent = πr l r = 6m, h = 8m Let slant height be = l We know that l2 = h2 + r2 l2 = "(8)2 + (6)2" l2 = "64 + " 36 l2 = 100 l = √100 l = √("102" ) l = 10 m Curved surface area of tent = πr l = (3.14×6×10) m2 = 188.4 m2 Now, Area of tarpaulin material = Area of tent (Length) × Breadth = Area of tent (Length) × 3 = Area of tent Length = 1/3 (Area of tent) = 188.4/3 = 62.8 m Length = 62.8 m Now, given that margin is 20 cm Total length = Length calculated + Margin = 62.8 m + 20 cm = 62.8 m + 20 × 1/100 m = 62.8 m + 0.2 m = 63 m

#### Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.