What is the volume of metal used in the pipe shown?
- 45pi cm^3
- 4500pi cm^3
- 18000pi cm^3
Explanation from PART66Online
The metal is the ring-shaped cross-section multiplied by the length. The radii are 5 cm and 4 cm, so the cross-section is pi x (5 squared - 4 squared) = 9 pi square centimetres, and the length is 5 m = 500 cm: V = 9 pi x 500 = 4500 pi cm^3. Using the diameters instead of the radii gives pi x (100 - 64) x 500 = 18000 pi, four times too much, and leaving the length as 5 instead of 500 cm gives 45 pi.
L
LugVonMises asked · 9 Mar 2018
If I use pi*(10^2 - 8^2)*500, the result is 18000pi. where is the error?
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