Cost of painting the inner curved surface = Rs. 8800
Cost of painting per square metre = Rs. 40
Hence, area that was painted =880040=220m2
⇒ inner curved surface area =220m2
We know the inner curved surface area of cylinder = 2πrh
Given: height of cylinder = 20 m
⇒2×227×r×20=220
⇒r=220×720×2×22
⇒r=1.75m
Hence, radius of the cylinder = 1.75 m