Question
Which of these is not a perfect cube?
Answer: Option D
:
D
By prime factorization, we have
343=7×7×71331=11×11×11512=8×8×881=3×3×3×3
For a number to be a perfect cube ,each of its factors must be repeated thrice.
343, 1331 and 512 are the perfect cubes of 7, 11 and 8 respectively, whereas 81 is not, as 3 is repeating 4 times which is not a triplet.
81 is not a perfect cube.
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:
D
By prime factorization, we have
343=7×7×71331=11×11×11512=8×8×881=3×3×3×3
For a number to be a perfect cube ,each of its factors must be repeated thrice.
343, 1331 and 512 are the perfect cubes of 7, 11 and 8 respectively, whereas 81 is not, as 3 is repeating 4 times which is not a triplet.
81 is not a perfect cube.
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