Convert the binary number 1101.101 to its decimal (base-10) value.
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A13.5
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B13.75
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C13.625
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D13.875
Answer
Correct Answer: 13.625
Explanation
Introduction / Context:Binary-to-decimal conversion requires positional weighting. Bits left of the point use powers of 2 with nonnegative exponents; bits right of the point use negative exponents. This problem includes both integer and fractional parts, so we convert each separately and then sum.
Given Data / Assumptions:
- Binary input: 1101.101
- Base: 2 (binary)
- Goal: Decimal value
Concept / Approach:For a binary value b3 b2 b1 b0 . b-1 b-2 b-3, the decimal value is sum(bi * 2^i). Compute integer and fractional contributions independently to avoid mistakes, then add them.
Step-by-Step Solution:
Integer part 1101 = 12^3 + 12^2 + 02^1 + 12^0Compute → 8 + 4 + 0 + 1 = 13Fractional part .101 = 12^-1 + 02^-2 + 12^-3Compute → 10.5 + 00.25 + 10.125 = 0.625Total decimal value = 13 + 0.625 = 13.625Verification / Alternative check:As a quick check, compare nearby options: 13.5 corresponds to .100, 13.75 corresponds to .11 (i.e., .110), and 13.875 corresponds to .111. Our fractional .101 equals 0.625, confirming 13.625.
Why Other Options Are Wrong:
- 13.5: Would require fractional part .100 (0.5), not .101.
- 13.75: Would require .11 or .110 (0.75), not .101.
- 13.875: Would require .111 (0.875), not .101.
Common Pitfalls:
- Reading .101 as 0.101 in decimal; digits are binary weights.
- Forgetting that each right-of-point bit halves the previous weight (2^-1, 2^-2, 2^-3, ...).
Final Answer:13.625