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 ` 12 ` ` per` ` m^2` , what will be the cost of painting all these cones? (Use π = 3.14 and take √ 1.04 = 1.02)

Explanation

We have, diameter = 40 cm
`therefore` Radius, `r=(40)/(2)=20 cm =(20)/(100)m=0.2m " " (because 1 cm = (1)/(100)m)`
and height = 1 m
`because l = sqrt(r^(2)+h^(2))`
`therefore l = sqrt((0.2)^(2)+1^(2))m=sqrt(0.04+1)m=sqrt(1.04)m=1.02 m`
Curved surface area of a cone ` = pi rl=3.14xx0.2xx1.02 m^(2)=0.64056 m^(2)`
Cost of painting per `m^(2) = Rs. 12`
Cost of painting per `m^(2) = Rs. 12`
Cost of painting `0.64056 m^(2) = Rs. 12xx0.64056 = Rs. 7.68672`
Cost of painting for 1 cone `= Rs. 7.68672`
Cost of painting 50 cones `= Rs. 7.68672xx50 = Rs. 384.336 = Rs. 384.34`