Base conversion — convert the octal number to decimal. Task: Find the decimal value of 74₈ by expanding with powers of 8.

Difficulty: Easy

Correct Answer: 60

Explanation:


Introduction / Context:
Octal (base 8) is often used as a compact representation of binary. Converting octal to decimal reinforces understanding of positional weights based on powers of 8.


Given Data / Assumptions:

  • Octal number: 74₈
  • Digits: 7 and 4 (valid octal digits 0–7)


Concept / Approach:
Expand using positional weights: the left digit is multiplied by 8^1 and the right digit by 8^0, then sum the results to get the decimal value.


Step-by-Step Solution:

8^1 = 8, 8^0 = 1Compute: 78 + 41 = 56 + 4Total = 60


Verification / Alternative check:
Convert 74₈ to binary: 7 → 111, 4 → 100; combined 111100₂ = 60₁₀, confirming the same result.


Why Other Options Are Wrong:

  • 74: confuses the symbol with its base-10 interpretation.
  • 22, 62, 58: incorrect arithmetic of octal expansion.


Common Pitfalls:

  • Including digits 8 or 9 in octal or misapplying decimal weights instead of powers of 8.


Final Answer:
60

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