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Chapter 6: Square Roots and Cube Roots > Finding Cube root through Prime Factorisation Method

Finding Cube root through Prime Factorisation Method

Consider 3375. Let's find its cube root using prime factorisation:

3375 = × × × × ×

= 33×53=3×53

Therefore, cube root of:

3375 = 33375 = × = (Enter factors in increasing order)

Similarly, to find 374088:

74088 = × × × × × × × × (Enter factors in increasing order)

= 23×33×73=2×3×73

Therefore,

374088 = × × =

Find the cube root of 8000

Prime factorisation of 8000 = × × × × × × × × (Enter factors in increasing order)

So,

38000 = 2 × 2 × 5 =

Find the cube root of 13824 by prime factorisation method.

13824 = × × × × × × × × × × × (Enter factors in increasing order)

= 23×23×23×33

Therefore,

313824= 2 × 2 × 2 × 3 =

Instructions

State true or false: for any integer m, m2 < m3. Why?

Let's consider four cases to check if the statement is true for all values. Case (i): m > 1 , Case (ii): m = 1 , Case (iii): m = 0 and Case (iv): m < 0.
Case (i) : m > 1. The statement is because m3 is than m2.
If m = 2, then 22 = 4 and 23 = 8 which gives us 4 8. Thus, m2 > m3.
Case (ii): m = 1. The statement is because m2 m3.
For m = 1, then 12 = 13.
Case (iii): m = 0. The statement is because m2 = m3.
For m = 0, then 02 = 03.
Case (iv): m < 0 (Negative Integers). The statement is because m3 m2.
If m = 2, then 22 = 4 and 23 = 8. So, 4 8.
Thus, the statement is not true for all integers m.