Karby

...didn't quite know where to ask this...though i suppose it could fit in here...

ok...i give up...so just how do you go about finding the nth root of a number without a calulator... for instance, the cube root of 27? yeah, it's 3, but how would you get that with just a pencil and some paper? ...i used to know, but i've been doing it with the calculator for so long, that i just...forgot. unlike your other basic math ops, it's not exactly something that's called for on a regular basis...

__________________
~my karma ran over my dogma.~

cchris

I pity you poor souls that have to know this stuff.
Work hard = $$$$$$$$$

Thats all I need to know.

GO HERE MY FRIEND

__________________
There's a fine line between participation and mockery

Karby

don't have to know it...just want to. i've just been thinking about for a while...thanx though.

__________________
~my karma ran over my dogma.~

Nisses

how do you get it for a square root? Might help for people here to jog their memory

(also: I'd like to know that as well )

The_Dude

bah, i used to know it too.

i can start this, but i dont konw if i'm doin it right

27^(1/3) = x
wouldnt u now turn this to log's?

__________________
"Luck is what happens when preparation meets opportunity." - Darrel K Royal

Nisses

ok, if it's just about whole powers that you want to take the n-th root of, then it's rather easy. (I actually jogged my own memory about that )

like The_Dude said, just take 27^(1/3) power. Now 27 is 3³
so you get 3^((1/3)*3) equals 3¨1 equals 3.

but as for numbers that aren't true powers... No idea.

__________________
Moderation should be moderately moderated.

tekaweni

Here's an easy to follow page that will help...

http://www.qc.edu.hk/it-school/homep...0Secondary.htm

__________________
If you always do what you've always done, you'll always get what you've always gotten

Lebell

You have to know the squares, cubes, whatever before you can start deriving roots.

Using your example, we know the cube root of 27 is 3, but suppose you asked what is the cube root of 28?

Well, we start by finding the nearest lower perfect cube, which is 27, and its root, which is 3.

So the first number of the cube root of 28 is 3, with a remander of 1.

next, what is the next lowest cube of 10 (1.0)? That is 8 or root 2, remainder of 2. (we are now at 3.2).

now what is the next lowest cube of 20 (.20)? That is still 8 or root 2, remainder 12 (we are now to 3.22)

what is the lowest cube of 120 (.120)? That is 64 or root 4, remainder 56 (we are now at 3.224)

and so on until you get the accuracy you desire.

__________________
"Of all tyrannies, a tyranny exercised for the good of its victims may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end, for they do so with the approval of their own conscience." – C. S. Lewis

The ONLY sponsors we have are YOU!

Please Donate!

Stiltzkin

Great link. My dad taught me how to do this a long time ago but I had forgotten.

__________________
The most important thing in this world is love.

Sleepyjack

thats pretty cool. I've never seen that before. As for numbers other than the square root (like that other method wouldn't work) all i can think of is using logs. Like if you had a log table and anti-log tale, or a calculator with only log functions and no root function.

anyways for the example its:

27^(1/3) = x

(1/3)log27 = logx

note: log27 = 1.43 (this is what you'd look up)

(1/3)*1.43 = logx

0.48= logx

note: the anti log is just 10 to the power of a number ie 10^
you'd also look this up!

10^.48 = x

3 = x

uncle phil

lebell explained it the way i learned it many, many years ago...

__________________
"We were wrong, terribly wrong. (We) should not have tried to fight a guerrilla war with conventional military tactics against a foe willing to absorb enormous casualties...in a country lacking the fundamental political stability necessary to conduct effective military and pacification operations. It could not be done and it was not done."
- Robert S. McNamara
-----------------------------------------
"We will take our napalm and flame throwers out of the land that scarcely knows the use of matches...
We will leave you your small joys and smaller troubles."
- Eugene McCarthy in "Vietnam Message"
-----------------------------------------
never wrestle with a pig.
you both get dirty;
the pig likes it.

CSflim

Yup! Just like long division!

__________________

uncle phil

and calculators were a thing of the future...(they used to teach us how to use our brains back then...)

__________________
"We were wrong, terribly wrong. (We) should not have tried to fight a guerrilla war with conventional military tactics against a foe willing to absorb enormous casualties...in a country lacking the fundamental political stability necessary to conduct effective military and pacification operations. It could not be done and it was not done."
- Robert S. McNamara
-----------------------------------------
"We will take our napalm and flame throwers out of the land that scarcely knows the use of matches...
We will leave you your small joys and smaller troubles."
- Eugene McCarthy in "Vietnam Message"
-----------------------------------------
never wrestle with a pig.
you both get dirty;
the pig likes it.

Karby

yes...i see now. thanx. thanx much

__________________
~my karma ran over my dogma.~

taog

I learned it this way not too many years ago.. and it works best!!!

You can actually set it up on your piece of paper like long division and it works great. It also keeps things organized when you are using crazy big numbers, and when you get into vectors and all that shit too. God i am glad i didn't continue with Algebra and Geometry.

guypunkr

Wow guys, I haven't done anything math related since I took my _____ (I don't want to sound like anything, so you can fill in whatever math you think I might've taken) as a juinor in high school, but after getting into all of this (I mean reading your helpful hints and stuff) I feel like pursuing math again. At least on my own...