SOLUTION: How do you uncube a number. For example, r cubed = 108.9. How do I find r? I have a graphing calculator that I can use but dont know which button i should even push. Thanks.

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Question 496568: How do you uncube a number. For example, r cubed = 108.9. How do I find r?
I have a graphing calculator that I can use but dont know which button i should even push. Thanks.

Answer by bucky(2189) (Show Source):
You can put this solution on YOUR website!
Here's one way to do it. In many cases you can even use just a cheap scientific calculator to do it.
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If you want to find the square root of a number you can raise the number to the one-half power (exponent = 1/2 or 0.5)
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If you want to find the cube root of a number you can raise the number to the one-third power (exponent = 1/3 or 0.333333333)
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If you want to find the fourth root of a number you can raise the number to the one-fourth power (exponent = 1/4 or 0.25)
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If you want to find the fifth root of a number you can raise the number to the one-fifth power (exponent = 1/5 or 0.20)
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And so on.
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On a cheap scientific calculator you might see if there is a key that says . If you see one, try doing this problem as follows: enter 108.9 and then press the key. Then enter 0.33333333 and finally press the "=" key. You should get the answer that the cube root of 108.9 is 4.775394914. (To check this answer, just enter it into and ordinary calculator, then multiply that number by itself, and then multiply it again by itself ... that is 4.775394914 times 4.775394914 times 4.775394914. You should get an answer that is very, very close to 108.9.)
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You don't need the graphing function of a graphing calculator. On my HP TI-89 I can just key in 108.9^0.333333333 and press the "enter" key to get the answer of 4.77539 (If more decimal places were needed, I would need to increase the number of significant displayed digits in the "Mode" function. I currently have the displayed digits set for "float 6" so I get a six digit answer with the decimal placed appropriately.)
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I hope this helps you understand a method that you can use to get various roots of a given number. Just divide 1 by the number of the root and then use that answer as the exponent which you raise the given number to. If you need further instructions, post your problem again.