Find the smallest number \(y\) such that \(y×162\) is a perfect cube.

2017

Find the smallest number \(y\) such that \(y×162\)  is a perfect cube.

  1. A.

    24

  2. B.

    27

  3. C.

    32

  4. D.

    36

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Correct answer: D

Answer: 36

  • Prime-factorize the given number: 162 = 2^1 × 3^4.

  • For a product to be a perfect cube, each prime's exponent must be a multiple of 3. Current exponents are: 2 → 1, 3 → 4.

  • Make each exponent a multiple of 3 by multiplying by the minimal additional powers: increase exponent of 2 from 1 to 3 (need 2 more factors of 2) and increase exponent of 3 from 4 to 6 (need 2 more factors of 3).

  • Thus y = 2^2 × 3^2 = 4 × 9 = 36.

  • Check: 162 × 36 = 2^3 × 3^6 = (2 × 3^2)^3 = 18^3, so the product is indeed a perfect cube.

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