Anyone good in maths?help

Question

This the question I got for math homework and I don't understand it. So the question is on chapter" cylinder" so the problem says "A cylindrical metal pipe has an external diameter of 6 cm and internal diameter of 4cm, the pipe is 1 metre long. Taking(pie)=3.14 find a)the volume of pipe in cm cubed and b) the mass of the pipe in kg, if 1 cm cubed of the metal weights 9 g" Ok so you can just explain how to do it or give me a link to a website that would help.

Answer 1

Volume = PI x radius² x length

External volume: 3.14 x 3² x 100 = 2826 cm³

Internal volume: 3.14 x 2² x 100 = 1256 cm³

Volume = 2826 - 1256 = 1570 cm³

Density = 0.009 kg/cm³ (slightly more dense than copper)

Mass = volume x density = 1570 x 0.009 = 14.13 kg (14.14 if you use a proper PI)

wat? - aganerd, Jan 25, 2011

^ - aganerd, Jan 25, 2011

do you know what pie is in that queston ? - aganerd, Jan 25, 2011

and do you write in the pi? - aganerd, Jan 25, 2011

do you write it in ? - aganerd, Jan 25, 2011

when i do the answer id different - aganerd, Jan 25, 2011

Answer 2

I think you need to review some basic geometry. The area of a circle = pi * radius ^ 2, where ^ 2 = squared. Pi is roughly 3.14, and you do have to multiply it.

The volume of a cylinder is the area of the circular base times the height (a.k.a. length): v = l * pi * r ^ 2.

To calculate the volume of metal in the pipe, calculate the volume of the pipe as if it were a solid cylinder, then calculate the volume of the air in the middle of the pipe, subtract the second from the first, and you get the volume of the metal in the pipe.

mass = volume * density

Remember to convert everything to the same unites. Centimeters work best here. Your answer will be in grams. You can convert to kilograms at the end, if you want to.

For reference, pi is the ratio of the circumference of a circle to it's diameter: pi = c / d.

Answer 3

I think what they are asking you to do is find the volume based on the internal diameter and the volume based on the outside diameter, subtract the internal volume (air) from the total volume (air plus pipe) to be left with the volume of the metal of the pipe, and then use the density and that volume to determine the mass of the pipe.