HOW TO FIND THE CUBE ROOT OF A NUMBER USING PRIME FACTORIZATION

The following steps would be useful to find the cube root of a number using prime factorization.

Step 1 : 

Write number inside the cube root as a product of prime numbers.

Step 2 : 

Write these numbers in triplets such that all three numbers in each triplet are equal.

Step 3 : 

We can take one number out of the cube root for every three same numbers multiplied inside the cube root.

Example 1 :

Find the cube root of 8.

Solution :

3√8 = 3√(2 x 2 x 2)

= 2

Example 2 :

Find the cube root of 27.

Solution :

3√27 = 3√(3 x 3 x 3)

= 3

Example 3 :

Find the cube root of 512.

Solution :

3512 = 3√(2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2)

3√[(2 x 2 x 2)(2 x 2 x 2)(2 x 2 x 2)]

= 2 x 2 x 2

= 8

Example 4 :

Find the cube root of (27 x 64).

Solution :

3(27 x 64) = 3√[(3 x 3 x 3)(2 x 2 x 2 x 2 x 2 x 2)]

= 3√[(3 x 3 x 3)(2 x 2 x 2)(2 x 2 x 2)]

= 3√[(3 x 3 x 3)(2 x 2 x 2)(2 x 2 x 2)]

= 3 x 2 x 2

= 12

Example 5 :

Find the cube root of 1000.

Solution :

3√1000 = 3√(2 x 2 x 2 x 5 x 5 x 5)

=3√[(2 x 2 x 2)(5 x 5 x 5)]

= 2 x 5

= 10

Example 6 :

Find the cube root of (8/125).

Solution :

3(8/125) = 3√8/3√125

=3√(2 x 2 x 2)/3√(5 x 5 x 5)

= 2/5

Example 7 :

Find the cube root of 0.008.

Solution :

3√0.008 = 3√(8/1000)

=3√8/3√1000

= 2/10

= 0.2

Example 8 :

Find the cube root of 0.027.

Solution :

3√0.027 = 3√(27/1000)

=3√27/3√1000

= 3/10

= 0.3

Example 9 :

Find the cube root of 0.343.

Solution :

3√0.343 = 3√(343/1000)

=3√343/3√1000

= 7/10

= 0.7

Example 10 :

Find the cube root of -125.

Solution :

3√-125 = 3√(-5 x -5 x -5)

= -5

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