The MINIMUM required for backbone floor to floor pathways is five (5) sleeves each being 103 mm (four trade size) in diameter. What increase in usable floor space should another 103 mm (four trade…

Question

Options

• A=929 m2 (10,001 ft2)
• B=1858m2 (20,001 ft2)
• C=3716 m2 (40,001 ft2)
• D=4645 m2 (50,001 ft2)

• A
  8% (2)
• B
  16% (4)
• C
  72% (18)
• D
  4% (1)

Explanation

Option C is correct because BICSI/TIA-569 standards specify that one additional 103 mm (4-inch trade size) floor-to-floor sleeve must be added for every 3,716 m² (approximately 40,000 ft²) increase - or fraction thereof - in usable floor space beyond the base allocation covered by the minimum five sleeves.

Why the distractors are wrong:

• A (929 m² / 10,001 ft²) - This figure (≈10,000 ft²) appears elsewhere in cabling standards (e.g., horizontal pathway sizing ratios), making it a tempting trap, but it is not the threshold for adding backbone floor-to-floor sleeves.
• B (1,858 m² / 20,001 ft²) - This is simply double option A; it has no basis in the sleeve-sizing rule and exists to catch test-takers who guess a midpoint.
• D (4,645 m² / 50,001 ft²) - This overshoots the correct increment by about 25%; the standard uses 3,716 m² / 40,000 ft², not 50,000 ft².

Memory tip: Use the "4–4–40" pattern - a 4-inch trade size sleeve, the 4th answer choice skipped, and an increment of 40,000 ft² (3,716 m²). Any time you see a 103 mm (4-inch) backbone sleeve question about additional capacity, anchor on 40,000 ft² as your trigger number.

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