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Mathematics - cube root
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Can any member provide a method for calculating a cube root for numbers with 4 or more digits, e.g., 2345, 23456, 234567 etc?
Answers
http:// www. wikihow. co... ate- Cube- Root- by- Hand
Having said that, found this which seems to work!
22:20 Sat 12th Nov 2011
2345
Take an estimate: say 12
Calculate 2345/(12 x12)
That is 16.285.
Add your estimate twice to 16.285. That is 40.285.
Divide that by 3: that gives 13.428
Repeat using 13.428 as your guess
2345/(13.428x13.428) = 13.005
Add that to 13.428 +13.428.
That gives 39.861
Divide it by 3. Gives 13.287
That is pretty much the cube root (I think the answer is 13.286)
Take an estimate: say 12
Calculate 2345/(12 x12)
That is 16.285.
Add your estimate twice to 16.285. That is 40.285.
Divide that by 3: that gives 13.428
Repeat using 13.428 as your guess
2345/(13.428x13.428) = 13.005
Add that to 13.428 +13.428.
That gives 39.861
Divide it by 3. Gives 13.287
That is pretty much the cube root (I think the answer is 13.286)
The tricks suggested, ie looking at the last digit, won't help as the OPer isn't asking just about cubes of integers. He gave example 2345 whiuch has a cube root 13.285593158578324, wich I found using http://www.csgnetwork...cuberootcubecalc.html
I assumed martinjr wanted a method for any number with more than 4 digits and had just used numbers with consecutive digits for his examples.
Hi the builder- what you say works the other way round but not always your way round. So yes if you take a number ending in 5 its cube will also end in 5
Similarly the cube of a number ending in 8 will end with a 2.
But it doesn't always work in reverse. The cube root of 2345 doesn't end in a 5 because the answer is not a whole number
Hi the builder- what you say works the other way round but not always your way round. So yes if you take a number ending in 5 its cube will also end in 5
Similarly the cube of a number ending in 8 will end with a 2.
But it doesn't always work in reverse. The cube root of 2345 doesn't end in a 5 because the answer is not a whole number
I've just returned to my thread right now (Sat 12th @17.46). Lots of interesting replies but factor30 is correct in assuming what I needed was a method for calculating the cube root of any number with more than 4 digits. I'm really only looking for the old arithmetic method which involved splitting the number into sets of three but the method escapes me. If it helps:- calculating the square root involves splitting the number into pairs and bringing down next pair alongside the remainder after finding the square of 1st pair of numbers. I know I've explained this badly so sorry about that.
Somethng like this http://xlinux.nist.gov/dads/HTML/cubeRoot.html ?
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