CBSE Notes, Lectures

CBSE - Mathematics - Surface Areas and Volumes

Surface Areas and Volumes

NCERT Exercise Exercise 13.3

What length of tarpaulin 3m wide will be required to make conical tent of height 8m and base radius 6m? Assume that the extra length of material that will be required for stitching margins and wastage in cutting is approximately 20cm (Use π = 3.14).

Radius of the base (r) = 6 m
Height of the conical tent (h) = 8 m
Let l be the slant height of the cone.
∴ l = √h+ r2
⇒ l = √8+ 62
⇒ l = √100
⇒ l = 10 m
CSA of conical tent = πrl
= (3.14 × 6 × 10) m2 = 188.4 m2
Breadth of tarpaulin = 3 m
Let length of tarpaulin sheet required be x.
20 cm will be wasted in cutting.
So, the length will be (x – 0.2 m)
Breadth of tarpaulin = 3 m
Area of sheet = CSA of tent
[(x – 0.2 m) × 3] m = 188.4 m2
⇒ x – 0.2 m = 62.8 m
⇒ x = 63 m

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