What is the 15's complement of the hexadecimal number (C00D0)16?

2018

What is the 15's complement of the hexadecimal number (C00D0)16?

Answer: B. (3FF2F)16ConceptFor an n-digit hexadecimal number, the 15's complement is formed by replacing every digit d with F − d, where F represents 15. This digitwise rule…

  1. A.

    (2FF3F)16

  2. B.

    (3FF2F)16

  3. C.

    (3EE2E)16

  4. D.

    (2EE3E)16

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Correct answer: B

Concept

For an n-digit hexadecimal number, the 15's complement is formed by replacing every digit d with F − d, where F represents 15.

This digitwise rule makes each original digit and its complement add to F without carrying to an adjacent position.

Application

  1. For the first digit C: F − C = 3.

  2. For each zero: F − 0 = F.

  3. For the digit D: F − D = 2.

  4. For the final zero: F − 0 = F.

  5. Keeping the original order gives (3FF2F)16.

Cross-check

Adding the original number and the complement gives (C00D0)16 + (3FF2F)16 = (FFFFF)16; every position sums to F, confirming the result.

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