# Planet Semirg and Planet Aniram

• September 23rd 2013, 09:51 PM
Planet Semirg and Planet Aniram
Planet Aniram is similar to Planet Semirg, both of which are perfect sphere. If the ratio of the length of Planet Aniram’s radius to the length of Planet Semirg’s radius is 3:4, then find the volume of Planet Semirg in cubic units if the volume of Planet Aniram is 135 cubic units.

I know how to find the ration, you divide by 3 but I don't know how to find the volume in cubic units.
• September 23rd 2013, 10:03 PM
votan
Re: Planet Semirg and Planet Aniram
The formula of the volume of a sphere is (4*pi/3)*R^3. You said you know how calculate the ratios. Can you continue from there?
• September 24th 2013, 05:19 AM
topsquark
Re: Planet Semirg and Planet Aniram
Nadeshikol, you need to start showing any work you've been able to do. If you haven't been able to we'll give some hints, but you have to show some effort as well. This refers to your other four posts as well.

-Dan
• September 24th 2013, 05:35 AM
HallsofIvy
Re: Planet Semirg and Planet Aniram
Assume planet Semirg's radius is R. What is its volume, in terms of R? Then planet Aniram's radius if (3/4)R. What is its volume, in terms of R? Divide the two volumes to find their ratio.
• September 24th 2013, 07:32 PM
Re: Planet Semirg and Planet Aniram
Quote:

Originally Posted by topsquark
Nadeshikol, you need to start showing any work you've been able to do. If you haven't been able to we'll give some hints, but you have to show some effort as well. This refers to your other four posts as well.

-Dan

I'm sorry! I will post any work I have done next time.
• September 24th 2013, 08:14 PM
Re: Planet Semirg and Planet Aniram
I got 268.16 cubic units as the answer.

Work:

V= 4/3*pi*4^3
V= 4/3*3.14/1=12.56/3
V=4.19*4^3
V=268.16
• September 24th 2013, 08:53 PM
votan
Re: Planet Semirg and Planet Aniram
Quote:

Originally Posted by Nadeshiko
I got 268.16 cubic units as the answer.

Work:

V= 4/3*pi*4^3
V= 4/3*3.14/1=12.56/3
V=4.19*4^3
V=268.16

Attachment 29291
• September 25th 2013, 07:51 PM
Re: Planet Semirg and Planet Aniram
Quote:

Originally Posted by votan

Hello! I don' think we have learned this kind of math yet. I mean the V and then a letter at the bottom.
• September 25th 2013, 08:03 PM
zzephod
Re: Planet Semirg and Planet Aniram
Quote:

Originally Posted by Nadeshiko
Planet Aniram is similar to Planet Semirg, both of which are perfect sphere. If the ratio of the length of Planet Aniram’s radius to the length of Planet Semirg’s radius is 3:4, then find the volume of Planet Semirg in cubic units if the volume of Planet Aniram is 135 cubic units.

I know how to find the ration, you divide by 3 but I don't know how to find the volume in cubic units.

Does not matter what the form of similar simple solids is the volume scales as the cube of any linear dimension. So if the radii are in the ratio $a:b$ the volumes are in the ratio $a^3:b^3$.

The condition that they are both perfect spheres is redundant, that they are similar is sufficient.

.
• September 25th 2013, 08:12 PM
votan
Re: Planet Semirg and Planet Aniram
Quote:

Originally Posted by Nadeshiko
Hello! I don' think we have learned this kind of math yet. I mean the V and then a letter at the bottom.

You used the V in your post of yesterday at 11:14 PM