Question

A cylinder is open at both ends and is made of 1.5-cm-thick metal. Its external diameter is 12 cm and height is 84 cm. What is the volume of metal used in making the cylinder? Also, find the weight of the cylinder if 1 cm ' of the metal weighs 7.5 g.

Answer 1

It is given in the question that, 

Thickness of the cylinder = 1.5 cm 

External diameter of the cylinder = 12cm 

Hence, 

Radius = 6 cm 

And, 

Internal radius = 4.5cm 

Height = 84cm 

Hence, 

We have the following measurements now, 

Total volume = \(\pi r^2h\)

= \(\frac{22}{7}\times4.5\times4.5\times84\)

= 5346 cm³

Hence, 

The volume of the metal = total volume – internal volume 

= 9504 – 5346 

= 4158 cm³ 

Therefore, 

Weight of the iron = 4158 × 7.5 

= 31.185 kg