Question

A $5$m wide cloth is used to make a conical tent of base diameter $14m$ and height $24m$. Find the cost of cloth used at the rate of $Rs.25$ per meter.

Answer 1

A] Let slant height be 'l' m.

n = 24 m

d = 14 m

$\therefore r=\frac{14}{2}=7m$

So,

$l^2=h^2+r^2$

$\Rightarrow l^2=(24{)}^2+(7{)}^2$

$=576+49$

$625$

$\therefore l=25m$

current surface area of cone

$=\pi rl$

$=\frac{22}{7}\times 7\times 25$

$=22\times 25$

$=550m^2$

length of cloth used = area / width

$=\frac{550}{5}$

$=110m$

As cost per m = Rs 25

$\therefore$ total cost $=110\times 25$

$=Rs2750$