How to Find Cube Root in Ti-84

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The powerful TI-84 remains one of the most enduring tools you'll find in any math class. Although its versatility obligates you to a certain amount of hunting and pecking through menus for the more complex functions, locating the cube root function is as simple as two key presses. The method for calculating cube roots is the same whether you're using the TI-84, TI-84 Plus or TI-84 Plus Silver.

Understanding Cubes and Cube Roots

Before you begin calculating cube roots, it's helpful to recall what happens when a number is cubed. If you cube any number, you multiply that number by itself three times. So to cube 4 (also written as 43), you'd multiply 4 × 4 × 4, which equals 64. To cube 5 (also written as 53), you'd multiply 5 × 5 × 5, which equals 125 and so on.

A cube root is simply the reverse operation, working backward from a number to discover which other number, multiplied by itself three times, gets you that original number. So the cube root of 125 is 5, because 53 = 125. Calculating cube roots by hand can be tiresome at best if you don't have them memorized, but calculating them with your calculator requires nothing more than a few keystrokes.

Finding Cube Roots on the TI-84, TI-84 Plus and TI-84 Plus Silver Edition

  1. Access the Cube Root Template

  2. Press the MATH key, followed by the 4 key. This opens the cube root template.

  3. Enter the Expression

  4. Enter the expression – that is, the number – you're evaluating the cube root of. Then press Enter to get your answer. If you entered 343 your calculator would return 7 as the answer because 73 = 343.

Calculating Other Roots on the TI-84

You can use a similar method to calculate other roots on the TI-84, TI-84 Plus or TI-84 Plus Silver Edition. You just need to select a different function from the MATH menu.

  1. Select the Root Template

  2. Press the MATH key, followed by the 5 key. This opens an undefined root template, which can be used for any index. The index is the small number that appears above and to the left of a root symbol for anything but a square root. It tells you how many times the mystery number had to be multiplied together to create the number underneath the root/radical sign.

  3. Enter the Index and Expression

  4. Enter the index of the root you want. You could enter 3 for a cube root, 4 for a fourth root and so on. Then press the right arrow key and enter the expression you want to evaluate. This is the number that goes under the radical sign. Press Enter to get your result.

    So, for example, if you entered 4 as the index to find the fourth root, then 81 as the expression to be evaluated, you'd end up with an answer of 3, because 34 = 81.


About the Author

Lisa studied mathematics at the University of Alaska, Anchorage, and spent several years tutoring high school and university students through scary -- but fun! -- math subjects like algebra and calculus.