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Contract AdminPreconstructionhard27% of exam part

When estimating drywall installation, a contractor calculates 2,400 square feet of wall area. After deducting openings and adding waste, the net quantity is 2,280 square feet. What waste factor was applied?

Correct Answer

D) Cannot be determined from given information

The waste factor cannot be determined because both opening deductions and waste additions affect the final quantity. The net result of 2,280 sq ft from 2,400 sq ft reflects both adjustments combined.

Answer Options
A
5%
B
10%
C
15%
D
Cannot be determined from given information

Why This Is the Correct Answer

The waste factor cannot be determined because we have two unknown variables affecting the final quantity simultaneously. We know the gross area (2,400 sq ft) and net area (2,280 sq ft), but we don't know how much area was deducted for openings (doors, windows, etc.) versus how much was added back for waste. The 120 sq ft difference represents the net effect of both deductions and additions, making it impossible to isolate the waste factor alone.

Why the Other Options Are Wrong

Option A: 5%

5% assumes we can calculate the waste factor, but we cannot separate the opening deductions from the waste additions with the given information.

Option B: 10%

10% assumes we can calculate the waste factor, but the 120 sq ft difference includes both opening deductions and waste additions combined.

Option C: 15%

15% assumes we can calculate the waste factor, but we need separate values for openings and waste to determine the actual waste percentage.

Memory Technique

Remember 'TWO UNKNOWNS = NO SOLUTION' - when both openings and waste affect the final quantity without separate values, you cannot isolate either factor

Reference Hint

Florida Building Code Chapter 25 - Gypsum Board and Plaster, or construction estimating references covering material takeoff procedures

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