Question

A 5 m wide cloth is used to make a conical tent of base diameter 14 m and height 24 m. Find the

cost of cloth used at the rate of Rs 25 per metre.

Answer 1

Given: Radius of base (r) and height (h) of the conical tank are 7 m and 24 m
⇒ Slant height (l) = r 2 + h 2 
                            =  (7 m) 2 + (24 m) 2 
                            = 49m 2 + 576m 2 
                            = 625m 2 
                            = 25m
Thus,
Curved surface area = πrl =  22 7 × 7 × 25 m 2 = 550m2

Now let x m of cloth is rquired
Then C.S.A of conical tank = area of cloth

⇒ 5x = 550
⇒ x =  550 5 = 110

Hence 110m of cloth is required to make the required conical tank.

Answer 2

pi * r * (r+l) = Total surface area
we need to find slant height, so
7^2 + 24^2 = 625 = 25^2
Therefore slant height = 25 m.
22/7 * 7 * 25+7
22*32 = 704m^2
704*25 = 17600 Rs
Therefore, cost of cloth will be 17600 Rs
Hope this helped! :P