Math Is Fun Forum

Hrslvr1612

Member

Registered: 2005-12-12

Posts: 13

I have no idea how to do these

19)Earth's diameter is about 3 2/3 time that of the moon. How do their volumes compare?

I know the answer is about 49.3 times the moon but i have no idea how to get that or where to start!

20) The sun's diameter is about 110 times that of the earth. How do their volumes compare?

And i dont know the answer to that one! Can you help me please!!!!! Thanky ou soooooo much!

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,423

Re: I have no idea how to do these

Hrslvr 1612,
The sun, earth and moon are also almost spherical in shape.
The volume of a sphere is given by the formula

where r is the radius, d is the diameter and pi is approximately 3.141592.
Since the volume is obtained by multiplying the cube of the radius by some factor,
it can be inferred that the volumes of two solids are proportional to the cubes of their radii or diameters (Since diameter= 2(radius)).
Therefore, the earth's volume would be

times the volume of the moon.

is approximately 49.3.

Similarly, since sun's diameter is approximately 110 times that of earth's,
the volume of the sun would be (110x110x110) times that of the earth, that is 1331000 times!

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