A cylindrical pipe 50m long with radius 7m has one end open. What is the total surface area of the pipe?

Analyze the question: A cylindrical pipe of length (height) h = 50 m and radius r = 7 m has one end open, so it has a curved surface and only one circular end (closed).

Concept:

• Curved surface area = 2πrh
• Area of one circular end = πr²
• Total surface area (one end open) = 2πrh + πr²

Solution:

Curved surface area: 2πrh = 2 × π × 7 × 50 = 700π m²

One circular end: πr² = π × 7² = 49π m²

Total surface area: 700π + 49π = 749π m²

Tip: Always check how many ends the cylinder has. Both ends closed: 2πr(h + r). One end open: 2πrh + πr². Both ends open: 2πrh. Option B (700π) is the trap for students who forget the closed end, since it is just the curved surface.