Radius (r) of cone = 40/2 = 20 cm = 0.2 m
Height (h) of cone = 1 m
CSA of each cone = πrl
= (3.14 × 0.2 × 1.02) m2 = 0.64056 m2
CSA of 50 such cones = (50 × 0.64056) m2
= 32.028 m2
Cost of painting 1 m2 area = Rs 12
Cost of painting 32.028 m2 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.