Question

An iron pillar has some part in the form of a right circular cylinder and remaining in the form of a right circular cone. The radius of the base of each of cone and cylinder is 8 cm. The cylinderical part is 240 cm high and the conical part in 36 cm high. Find the weight of the pillar if one cu. cm of iron weighs 7.8 grams.​

Answer 1

${\sf{\purple{\underline{\overline{Given:-}}}}}$

• Radius = 8 cm
• Height of cylinder = 240 cm
• the conical part in 36 cm high.

${\sf{\pink{\underline{\overline{To \: find:-}}}}}$

Weight of the pillar if one cu. cm of iron weighs 7.8 grams.

${\sf{\purple{\underline{\overline{Solution :-}}}}}$

$\sf \fbox \red {We know that}$

• Volume of cylinder = πr²h
• Volume of cone = ⅓πr²h

Now,

Volume of cylinder = 3.14 × 8 × 8 × 240

• => 48320.4 cm^3

Now,

• ⅓ × 3.14 × 8 × 8 × 36
• 1 × 3.14 × 8 × 8 × 12
• 3.14 × 64 ×12
• 2411.52 cm^3

Now,

Weight of pillar = Volume of cylinder + volume of cone

• W = 48320.4 + 2411.52
• W = 50730

Now,

• 1kg = 1000gm
• 7.8/1000 × 50730
• 0.0078 × 50730
• 395.4 kg
• Weight of pillar is 395 kg.

${\sf{\purple{\underline{\overline{❀Tʜᴀɴᴋs!!}}}}}$

Answer 2

Answer:

$395 \: kg$

Explanation:

We know that:-

Volume of cylinder = πr²h

Volume of cone = ⅓πr²h

Now,

Volume of cylinder = 3.14 × 8 × 8 × 240

=> 48320.4 cm^3

Now,

⅓ × 3.14 × 8 × 8 × 36

1 × 3.14 × 8 × 8 × 12

3.14 × 64 ×12

2411.52 cm^3

Now,

W = 48320.4 + 2411.52

W = 50730

Now,

1kg = 1000gm

7.8/1000 × 50730

0.0078 × 50730

395.4 kg

Weight of pillar is 395 kg.