In a hot water heating system, there is a cylindrical pipe of length 28 m and diameter 5 cm. Find the total radiating surface in the system.

Radis of cylindrical pipe r = 5/2 cm = 2.5 cm = 0.025 m and lenght h = 28 m
Total surface area of cylindrical pipe = 2πr (r + h)
= 2 × 22/7 × 0.025 × (0.025 + 28) = 2 × 22/7 × 0.025 × 28.025 = 4.4 m² (approx)
Hence, the total radiating surface in the system is 4.4 m².