15. A hollow cylindrical copper pipe is 21 m long. Its outer and inner diameters are 10 cm and 6 cm the total surface area of the solid thus generated. respectively. Find the mass of the copper used in making the pipe if mass of 1³cm copper is about 9 g.
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Answer:
3360cm
Step-by-step explanation:
Length or height of pipe=210cm
Outer diameter =10cm ⇒ outer radius =5cm
Inner diameter=6cm ⇒ inner radius=3cm
Volume of copper used= Volume of cylinder
=π(r
2
2
−r
1
2
)×h
=π(5
2
−3
2
)×210cm
3
=
7
22
×210×(5+3)×(5−3)cm
3
=3360cm
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