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 m2, what will be the cost of painting all these cones? (Use π = 3.14 and take √1.04 = 1.02)
Radius of the cone (r) = 40/2 cm = 20 cm = 0.2 m
Height of the cone (h) = 1 m
Let l be the slant height of a cone.
∴ l = √h2 + r2
⇒ l = √12 + 0.22
⇒ l = √1.04
⇒ l = 1.02 m
Rate of painting = rs12 per m2
Curved surface of 1 cone = πrl m2
= (3.14 × 0.2 × 1.02) m2
= 0.64056 m2
Curved surface of such 50 cones = (50 × 0.64056) m2
= 32.028 m2
Cost of painting all these cones = rs(32.028 × 12)
= rs 384.34
