Question

20. Which of the following numbers are not perfect cubes?
(ii) 216
(iii) 243
(iv) 1728
For each of the non-perfect cubes
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Answer 1

Answer:

216 = 2 × 2 × 2 × 3 × 3 × 3 = 2 3  × 3 3

Each prime factor is appearing as many times as a perfect multiple of 3,

therefore, 216 is a perfect cube.