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If a metal pipe 10cm long has an external diameter of 12c...

If a metal pipe 10cm long has an external diameter of 12cm and a thickness of 1cm find the volume of the metal used in making the pipe

A.

120\(\pi\)cm3

B.

110\(\pi\)cm3

C.

60\(\pi\)cm3

D.

50\(\pi\)cm3

Correct answer is B

The volume of the pipe is equal to the area of the cross section and length.

let outer and inner radii be R and r respectively.

Area of the cross section = (R2 - r2)

where R = 6 and r = 6 - 1

= 5cm

Area of the cross section = (62 - 52)\(\pi\) = (36 - 25)\(\pi\)cm sq

vol. of the pipe = \(\pi\) (R2 - r2)L where length (L) = 10

volume = 11\(\pi\) x 10

= 110\(\pi\)cm3