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

For Conical tent,
b=5m
radius r = diameter/2 =14/2=7m
height h=24 m
slant height l = √((h^2)+(r^2))=√(576)+(49)=√625=25
C.S.A of tent= πrl
=(22/7)×7×25
=550 m^2
Area of cloth required = C.S.A of tent
l×b=550
l×5=550
l=110m
Cost of 1 m cloth=₹25
Cost of 110 m cloth=₹(110×25)=₹2750

Answer 2

let the length of cloth be l mts

then according to problem,

area of cloth =CSA of cone of radius 7 m and height 24 m

slant height, l = ?

l2 = h2 + r2 = 576 + 49 = 625
so, l = 25 m
area of cloth = pie * r * l = (22/7) * 7 * 25 = 550 m2 
so, length * width = 550
so, length = 550/5 = 110 m
cost of 1 m cloth = Rs. 25
cost of 110 m cloth = Rs. (110 * 25) = Rs. 2750