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Microsoft Excel: Raise a Number to a Fraction to Find the Square or Third Root

written by: Mr Excel•edited by: Michele McDonough•updated: 7/6/2011

Problem: Excel offers a SQRT function to find the square root of a number. What if you need to figure out the third root or the fourth root?

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    Strategy: You can raise a number to a fraction to find a root. To find the square root of a number, you can raise the number to (1/2). To find the cube root of a number, you can raise the number to (1/3). To find the eighth root of a number, you can raise the number to (1/8).

    Here are several examples.

    If you need to find the square root, you can use the SQRT function, as shown in Fig. 436. (Click any image for a larger view.)

    As shown in Fig. 437, you can also raise the number to the one-half (1/2) power. Or, you can raise the number to 0.5, as shown in Fig. 438.

    To find the cube root of a number, you can raise the number to the one third (1/3) power, as shown in Fig. 439.

    To find the fourth root of a number, raise the number to either one-forth (1/4) or 0.25 power, as shown in Fig. 440 and Fig. 441, respectively. To find the seventeenth root of a number, raise it to the one-seventeenth (1/17) power, as shown in Fig. 442.

    Summary: Although Excel only offers a function for a square root, you can use the technique of raising to a fractional power in order to determine any root of a number.

    Commands Discussed: Exponent operator

    Functions Discussed: =SQRT()

    See all Microsoft Excel tips

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    Images

    Fig. 436Fig. 437Fig. 438Fig. 439Fig. 440Fig. 441Fig. 442
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    References and Additional Resources

    If you're looking for more tips and tutorials, check out 91 Tips for Calculating With Microsoft Excel. This collection of easy-to-follow guides shows how to customize charts and graphs, different ways to make complex spreadsheets easier to update, and even how to play games like Craps in Excel.

    Other Resources:

    Microsoft Excel Official Site, http://office.microsoft.com/en-us/excel/

    Bill Jelen, Microsoft Excel 2010 In Depth, Available from Amazon.com.