Question

A bus stop is barricaded from the remaining part of the road by using 50 hollow cones made of recycled cardboard. Each cone has a base diameter of 40 cm and height 1 m. If the outer side of each of the cones is to be painted and the cost of painting is Rs.12 per $m^2$, what will be the cost of painting these cones? (Use $\pi =3.14and\sqrt{1.04}=1.02)$

Answer 1

Diameter of the base of tent =40 cm

$\therefore Radiusofthebaseofcone\left(r\right)=\frac{40}{2}=20cm=0.2m$

Height (h)=1 m= 100 cm

$\therefore Slantheight\left(l\right)=\sqrt{r^2+h^2}=\sqrt{(20{)}^2+(100{)}^2}=\sqrt{400+10000}=\sqrt{10400}cm=102cm\left(approx\right)=1.02m$

Now curved surface area of one cone=$\pi rl$=$3.14\times 0.2\times 1.02m^2=0.64056m^2$

Curved surface area of 50 such cones =$0.64056\times 50=32.028m^2$

Rate of painting =Rs.12 per $m^2$

$\therefore Totalcost=Rs.32.028\times 12=Rs.384.336=Rs.384.34$