Question

a cylinder is open at both ends and us made of 1.5 cm thick metal. it's 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 cm³ of the metal weighs 7.5 g​

Answer 1

Answer: 11576.25 g = 11.57625 kg

Step-by-step explanation:

We have,

external diameter =12 cm

so, external radius r = 6 cm

area of its external base = r² * 3.5 = 36 cm² *3.5= 126 cm²

And height = 84 cm

so, volume of the cylinder including the volume of the metal =area of it's external base * height = 126 cm² * 84 cm

= 10584 cm³

Now,

internal diameter of the cylinder = 12 cm - 1.5 cm = 10.5 cm

internal radius r = 10.5 cm /2 = 5.25 cm

area of the internal base = r² * 3.5 = 5.25 cm * 3.5 = 18.375 cm²

so, volume of the cylinder excluding the volume of the metal = area of the internal base * height

=18.375 cm² * 84 cm

=1543.5 cm³

Now, we have,

weight of 1 cm³ = 7.5 g

so, weight of 1543.5 cm³ = 7.5 g * 1543.5

= 11576.25 g

= 11.57625 kg