A cube, or cubic number, is formed by multiplying another number by itself and then by itself again. A "cube root" is the name given to the other number from which the cube is formed.

Imagine a Rubik's cube. Each edge of the Rubik's cube has three tiles. Then three multiplied by three, multiplied by three again is 27, the number of little units that make up the full Rubik's cube. So "three cubed" is 27, or put another way, 3 is the cube root of 27.

Now our question is about -27. This time -3 multiplied up is the answer. -3 times -3 is +9. Then +9 times -3 gives -27.

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