If LCM of 8, 12 and K is 144, then what is the value of K?

2021

If LCM of 8, 12 and K is 144, then what is the value of K?

  1. A.

    12

  2. B.

    144

  3. C.

    18

  4. D.

    48

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Correct answer: B

Solution: Use prime factorizations and the definition of LCM.

  • Prime factorizations: 8 = 2^3; 12 = 2^2 × 3; 144 = 2^4 × 3^2.

  • LCM of 8 and 12 is 24 = 2^3 × 3.

  • We need K such that LCM(24, K) = 144. For each prime, the exponent in the LCM is the maximum of its exponents in the numbers being combined. So the exponent of 2 in K must be 4 (since max(3, exp2(K)) = 4) and the exponent of 3 in K must be 2 (since max(1, exp3(K)) = 2).

  • Thus K = 2^4 × 3^2 = 144.

Answer: 144

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