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Home › Digital Electronics › In 8421 BCD addition, if a 4-bit digit sum is greater than 1001₂ (decimal 9), which binary correction is added to obtain a valid BCD result?
MCQ Practice Question
Digital ElectronicsBCD Arithmetic

In 8421 BCD addition, if a 4-bit digit sum is greater than 1001₂ (decimal 9), which binary correction is added to obtain a valid BCD result?

  • A0011
  • B0110
  • C1001
  • D1010
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Correct Answer: B. 0110
Explanation: A BCD digit is valid only from 0000 through 1001. When the binary digit sum exceeds 9, adding 0110₂ corrects the result and generates the appropriate decimal carry.
Reference: Standard digital electronics: BCD addition
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