Question

a hollow cylindrical metallic pipe is 21 cm long if the external and internal diameter of the pipe at 12 cm and 8 cm respectively find the volume of metal used in making the pipe​

Answer 1

Answer:

Given, the height of the hollow cylinder h=21cm

The inner diameter of hollow cylinder=6cm

And the outer diameter=10 cm

Then we have to find the volume of the metal used in making the pipe.

We know that Radius=Diameter2

Then inner radius r=62=3cm

And the outer radius R=102=5cm

Then volume of inner cylinder=πr2h

On putting the given values we get,

⇒ Volume of inner cylinder=227×(3)2×21

On solving we get,

⇒Volume of inner cylinder=22×9×3=594cm3

And the volume of outer cylinder=πR2h

On putting the given values we get,

⇒Volume of outer cylinder=227×(5)2×21

On solving we get,

⇒Volume of outer cylinder=22×25×3=1650cm3

Now the volume of metal used in the making of pipe=Volume of outer cylinder-volume of inner cylinder

On putting the values we get,

The volume of metal used in the making of pipe=1650−594

The volume of metal used in the making of pipe=1056 cm3

Answer- The correct answer is B.

Note: You can directly use the formula of hollow cylinder which is given as-

Volume of hollow cylinder=πh(R−r) where h is the height of the cylinder, R is the outer radius and r is the inner radius to find the volume of metal used to make the cylindrical pipe because the volume of metal used will be equal to the volume of the hollow cylinder.

Answer 2

Answer:

Refer to the attachment

hope it's helpful for you ✌️✌️

❤️ XxItzriyooxX❤️