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Railways Quantitative Aptitude Basic Calculations Sample Paper Square Roots & Cube Roots Sample Test Paper-5

  • question_answer
    The smallest number which when multiplied with 7200 will make the product a perfect cube, is

    A)  10

    B)                     20

    C)  30                   

    D)  None of these.

    Correct Answer: C

    Solution :

    [c] Expressing 7200 as its prime factors \[7200=2\times 2\times 2\times 2\times 2\times 3\times 3\times 5\times 5\] \[7200=(2\times 2\times 2)\times (2\times 2)\times (3\times 3)\times (5\times 5)\] We find that prime factors 2, 3 & 5 appear in groups of two, so to make the given no. perfect cube, we must multiply it with \[2\times 3\times 5=30\]


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