Question

A hollow cylindrical pipe is 21 dm long. Its outer and inner diameters are 10cm and 6cm respectively. Find the volume of copper used in making the pipe.

Answer 1

Height,h=21 dm=210 cm
Outer radius,r1=5 cm
Inner radius,r2=3 cm
Therefore,
Volume=$\pi$${ (r1)^{2} - (r2)^{2} }h$
=22/7*(25-9)*210
=10560 centimeter cube.

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Answer 2

AnswEr:

We have,

• h = height of the cylindrical pipe = 21 dm = 210 cm

• R = External Radius = $\tt\dfrac{10}{2}cm=5cm$

• Internal Radius = $\tt\dfrac{6}{2}cm\:=3cm$

___________________________

$\tiny\star\sf\underline{volume\:\:\:of\:\:\:the\:\:\:copper\:\:\:used\:\:\:in\:\:\:making\:\:\:the\:\:\:pipe}$

= Volume of the external radius - Volume of the internal cylinder

$\sf \: = \pi {r}^{2} h - \pi {r}^{2}h = \pi \: ( {r}^{2} - {r}^{2} )h \\ \\ \sf = \frac{22}{7} \times ( {5}^{2} - {3}^{2} ) \times 210 \: {cm}^{3} \\ \\ \sf = \frac{22}{7} \times 16 \times 210 \: {cm}^{3} \\ \\ \sf = 10560 \: {cm}^{3}$