A bus stop is barricaded from the remaining part of the road, by using 50 hollow cones made of recycled card-board. Each cone has a base diameter of 40cm and height 1m. 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 `(U s epi=3. 14a n dsqrt(1. 04)=1. 02))`

Explanation

Since the outer side of each cone is to be painted, the area to be painted will be equal to the curved surface area of the cone.
The curved surface area of a right circular cone with base radius(r) and slant height(l) is `pirl`
Slant height,
`l = √(r² + h²)` where h is the height of the cone.
Diameter, `d = 40cm = 40/100 m = 0.4m`
Radius, `r = 0.4/2m = 0.2m`
Height, `h = 1 m`
Slant height, `l = sqrt(0.2)^2 + (1)^2`
`= sqrt0.04 m^2 + 1 m^2`
`= sqrt1.04 = 1.02m (given)`
The curved surface area `= pirl`
`= 3.14 xx 0.2m xx1.02m`
`= 0.64056 m^2`
`Curved surface area of 50 cones = 50 × 0.64056 m^2 = 32.028 m^2`
`Cost of painting of 50 cones at ₹ 12 per m^2= 32.028xx12`
`=384.34`rupees.
Thus, the cost of painting all the cones is `384.34`rupees