Question

The cost of canvas required for a conical tent, of height $8m$ and diameter of the base $12m$, at the rate of Rs $3.50$ per $m^2$ is

• A. Rs $620$
• B. Rs $600$
• C. Rs $640$
• D. Rs $660$

Answer 1

The correct option is D Rs $660$

$\Rightarrow$ Radius of conical tent $\left(r\right)=\frac{12}{2}=6m$

$\Rightarrow$ Height of conical tent $\left(h\right)=8m$

$(l{)}^2=(r{)}^2+(h{)}^2$ [ By Pythagoras theorem ]

$\Rightarrow$ $(l{)}^2=(6{)}^2+(8{)}^2$

$\Rightarrow$ $(l{)}^2=36+64$

$\Rightarrow$ $(l{)}^2=100$

$\therefore$ $l=10m$

$\Rightarrow$ Surface area of conical tent $=\pi rl$

$=\frac{22}{7}\times 6m\times 10m$

$=188.57m^2$

$\Rightarrow$ The cost of canvas $=Rs(188.57\times 3.50)$

$=Rs.660$