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 all these cones?

`("Use "π = 3.14" and take "sqrt1.04= 1.02)`

#### Solution

Radius (*r*) of cone = 40/2 = 20cm = 0.2m

Height (*h*) of cone = 1 m

Slant height (*l*) of cone`= sqrt(h^2+r^2)`

`=[sqrt((1)^2+(0.2)^2)]m=sqrt1.04m=1.02m`

CSA of each cone = π*rl*

= (3.14 × 0.2 × 1.02) m^{2} = 0.64056 m^{2}

CSA of 50 such cones = (50 × 0.64056) m^{2}

= 32.028 m^{2}

Cost of painting 1 m^{2} area = Rs 12

Cost of painting 32.028 m^{2} area = Rs (32.028 × 12)

= Rs 384.336

= Rs 384.34 (approximately)

Therefore, it will cost Rs 384.34 in painting 50 such hollow cones.