Question

Difficulty: MediumNumber Bases and Conversions

Convert the decimal number 18.6251018.625_{10} to a number in base 8. What is the equivalent value in base 8?

  1. 22.5822.5_8Answer
  2. B
    22.625822.625_8
  3. C
    24.5824.5_8
  4. D
    22.4822.4_8

Answer

The equivalent value in base 8 is 22.5822.5_8.
Converting the whole number part 181018_{10} to base 8 gives 22822_8 because 18=2×81+2×8018 = 2 \times 8^1 + 2 \times 8^0. Converting the fractional part 0.625100.625_{10} to base 8 involves multiplying by 8: 0.625×8=5.00.625 \times 8 = 5.0, giving .58.5_8. Thus, 18.62510=22.5818.625_{10} = 22.5_8.

Step-by-Step Solution

1
Convert the integer part (1818) from base 10 to base 8.
18÷8=218 \div 8 = 2 with a remainder of 22. Reading the digits upwards gives 22822_8.
Successive division by 8 extracts the octal place values for the whole number.
2
Convert the fractional part (0.6250.625) from base 10 to base 8.
0.625×8=5.00.625 \times 8 = 5.0. The whole number part of the product is 55, so 0.62510=0.580.625_{10} = 0.5_8.
Successive multiplication of the fractional part by the target base isolates the negative powers of the base.
3
Combine the converted integer and fractional parts.
228+0.58=22.5822_8 + 0.5_8 = 22.5_8.
The full representation is the sum of the integer and fractional base 8 components.

Key Concept

Fractional Base Conversion
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