Mathematics

nsfrustratesme · Veteran Member

Mathematics

nsfrustratesme · Veteran Member

Also, i was wondering if anyone knows of another site like this, but for Mathematics or Calculator Apps., because that would be really cool.

sharpobject · Star Member

We learned geometric mean for only 2 numbers, so I may be wrong in saying this. The geometric mean for a set of n numbers is (the product of the numbers)^(1/n).

A brief visit to Wikipedia confirms the above, and gives the equation for harmonic mean. I found it was the formula for combined electric resistance, multiplied by the number of resistors. The harmonic mean expressed in words is, for a set of n numbers, n divided by the sum of the inverses of the numbers.

If that didn't get you anywhere, see Wikipedia's harmonic mean and geometric mean.

Edit: Yes, the arithmatic mean is the average. Sorry, I don't know of any math or calculator sites.

-- Edited by sharpobject at 17:37, 2005-04-06

Mathman · Star Member

Yes the geometric mean is the formula as posted above.

Here are two examples:

For two numbers-

Geometric mean of 4 and 9 is (4 x 9)^0.5 = (36)^0.5 = 6

where ^0.5 is the square root of the product of the 2 numbers

For three numbers-

Geometric mean of 2, 4, and 64 is (2 x 4 x 64)^0.3333 = (512)^0.3333=8

where ^0.3333 is the cube root of the product of the 3 numbers

and so on.

Date: Apr 6, 2005

Harmonic mean is easy once you master the concept...

take the reciprocals of the numbers, add them, divide that number by two, and then take the reciprocal of that.

Basically, the harmonic mean is the reciprocal of the arithmetic mean of the reciprocals.

Hope this helps,

Vinay

Penguinzchaseme · Veteran Member

Not completely correct:

To find the Harmonic mean of N numbers, add the recipricols of all of the numbers, divide that number by N, and take the recipricol of that.

Note, for mathematics test you will usually get G and A, where G is the Geometric mean and A is the arithmetic mean. The harmonic mean, H, of N numbers is:

G^2/A

nsfrustratesme · Veteran Member

Awesome, thanks guys. I'll probably have some more questions later on, but that helps a lot.

webmaster · Administrator

Very true!

When I developed this forum, I wanted it to be used as a UIL Math Forum, where we can discuss any form of UIL math related questions. Don't be afraid to ask about calculator questions, math questions, number sense questions, or even computer science questions. I have no problem with that.

Keep in mind, my "expertise" (if you can call it that) is basically in number sense, but we are all here to help each other out. So please, ask away! It could only get better with the more people we have, so invite others to join in the conversations.

Thanks!

Date: Apr 8, 2005

Penquinz...

did you mean (G^2)/A

or G^(2/A) ?

Thanks a lot for your help

Penguinzchaseme · Veteran Member

Sorry for the ambiguity:

(G^2)/A

Full reference can be found here:mathworld.wolfram.com/HarmonicMean.html

Date: Apr 8, 2005

One thing, though...

That formula: (G^2)/A only works when you have two numbers.

I wonder if when you are given three numbers, you could use (G^3)/(A^2)?

I think I'll check that out...

Vinay

sharpobject · Star Member

numbers: 7, 8, 12
harmonic mean: 504/59=8.54
(G^3)/(A^2): 896/243=3.69
Not quite, sorry.

Great idea, though. Also, for a set of N numbers, N>2, (G^N)/(A^(N/2)) doesn't give the harmonic mean. I tried a few other things, there seems to be no other way than to actually take the harmonic mean when dealing with more than two numbers.

nsfrustratesme · Veteran Member

I guess this is mainly for calculators, but it could be on the math test too. I was wondering if someone could help me out with like.... lots of formulas. I know the basic ones, and i know spheres, but there's a lot i don't know (frustrums, square pyramids, etc.) If yall could help me out with like.. surface area, volume, diagnal, etc. that would be awesome. Thanks in advance.