another problem..

[maeveoneill]

A silo has a cylindrical main section and a hemispherical roof. If the height of the main section is 10m, what should the radius be in order that the volume of the islo (including the part inside the roof section) is 2000m^3?

could someone help me start off with the equation. I Want to figure out the rest on my own so please dont give it away. Thank you!

 

[stapel]

The volume of a right circular cylinder with radius "r" and height "h" is:

. . . . .V_cyl. = (pi)(r²)(h)

The volume of half of a sphere with radius "r" is:

. . . . .V_hemi. = (2/3)(pi)(r³)

You have been given the value for "h". You know that:

. . . . .V_silo = V_cyl. + V_hemi.

And you have the value for V_silo. So form the equation, plug in the given values, and solve for the radius "r".

Eliz.

 

[maeveoneill]

2000= [(pi)(r²)(10)][(2/3)(pi)(r³)]
= (31.42r²)(2.09r³)
= 65.67r^5
30.46= r^5
1.98= r

what is wrong wit that? the answer is supposed to be 6.64m^3

 

[stapel]

Why are you multiplying the volumes instead of adding them?

Eliz.

 

[maeveoneill]

ahh stupid me. but how do you add r² and r^3.. ooh .. wait nvm thank you!!