A hollow iron pipe is 35 cm long. Its outer diameter is 20 cm and its inner diameter is 16 cm. Find the volume of iron in the pipe, in cubic centimetres. (Take π = 22/7.)

Question

Accepted Answer

3960. Outer radius R = 10 cm, inner radius r = 8 cm. Iron = outer cylinder − inner cylinder = \π h (R^2 - r^2) = 22/7(35)(100 - 64) = 110 × 36 = 3960 cm³. 11000 is the outer cylinder alone (forgetting that the pipe is hollow); 7040 is the hollow space; 440 comes from writing (R - r)^2 = 4 instead of R^2 - r^2 = 36 .

A hollow iron pipe is 35 cm long. Its outer diameter is 20 cm and its inner diameter is 16 cm. Find the volume of iron in the pipe, in cubic centimetres. (Take π = 22/7.)

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