alleryWhich of the following numbers is NOT a perfect cube?
A64
B243
C216
D1728
Answer & Solution
Correct answer: B. 243
1. 64 = 4³, 216 = 6³ and 1728 = 12³, all perfect cubes.
2. For 243, note 6³ = 216 and 7³ = 343, so 243 lies between consecutive cubes.
3. Hence 243 is not a perfect cube (it is actually 3⁵).
_Source: RRB Group D (RRC) PYQ, held 27-10-2013, Q.40._
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