2017 · Q73
A ball of radius 1 cm is put into a cylindrical pipe so that it fits inside the pipe. If the length of the pipe is 14 m, what is the surface area of the pipe ?
Elementary MathematicsMensuration
- A2200 square cm
- B4400 square cm
- C8800 square cm
- D17600 square cm
Explanation
The ball fixes the pipe's inner radius at 1 cm; length 14 m = 1400 cm. Lateral surface area = 2πrh = 2×(22/7)×1×1400 = 8800 cm²: option C. (UPSC's official key accepts C or D for this item; D = 17600 double-counts.)