ITPEC FE Subject A April 2026 Question 2
ITPEC FE Subject A April 2026 — Question 2 of 60
668.25 — expand each octal digit by its power of 8.
Integer part: 1×8³ + 2×8² + 3×8¹ + 4×8⁰ = 512 + 128 + 24 + 4 = 668
Fraction part: 2×8⁻¹ = 2/8 = 0.25
Total: 668 + 0.25 = 668.25
Answer (b)
Why not others:
- (a) 27.0 — far too small; the leading digit alone already contributes 1×8³ = 512
- (c) 1542.5 — matches no consistent place-value expansion of 1234.2 in base 8
- (d) 5346.0 — too large for four octal digits (the maximum, 7777₈, is 4095) and it drops the fraction
Key rule: Digits left of the point use 8⁰, 8¹, 8²… moving outward; digits right of it use 8⁻¹, 8⁻²…. The same method works for any base — only the base value changes.
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