Home >> Science & Nature >> Numerology

How to Determine the Cube Root of a Number

When a number is multiplied by itself three times, it is cubed. The cube root of that number is the original number that was cubed. For example, five cubed is five times five times five, which equals 125. The cube root of 125 is five. The cube roots of numbers can easily be found using a calculator. Finding cube roots without a calculator is a little harder.

Instructions

- 1
  Memorize the cubes of the digits 1 through 9: 1, 8, 27, 64, 125, 216, 343, 512, 729.
- 2
  Drop the last three digits of a number and find the largest cube contained in the remaining digits. This number is the tens digit. For example, if the number is 79,507, drop the 507. Then determine the largest cube of 79, which is four. (Four cubed equals 64.) The tens-digit of the cube root is four.
- 3
  Look at the last number of the three digits dropped in Step 2. Whichever cube (from digits one through nine) has the same ending, this number is the ones place. For example, using the number 79,507 from Step 2, the last number of the last three digits is seven. Seven is the ending of three cubed (27), so three is the ones place. The cube root of 79,507 is 43.

Numerology