Base conversion — convert the octal number to decimal. Task: Find the decimal value of 74₈ by expanding with powers of 8.
Electronics
Number Systems and Codes
Difficulty: Easy
Choose an option
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A74
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B60
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C22
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D62
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E58
Answer
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 = 60Verification / 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