A cricket drains 36 ft from its high point to a roof drain at a taper of 1/4 in. per foot. What thickness change occurs over that run?
Correct Answer
D) 9 in.
The taper changes 36 ft x 1/4 in./ft = 9 in. Other choices use a shorter run, round to a convenient board thickness, or use 1/3 in. per foot.
Why This Is the Correct Answer
The taper changes 36 ft x 1/4 in./ft = 9 in. Other choices use a shorter run, round to a convenient board thickness, or use 1/3 in. per foot.
Why the Other Options Are Wrong
Option A: 6 in.
tapered insulation, choice b: 6 in. backs into 24 when divided by 1/4; the accepted setup gives 36 on that same base.
Option B: 8 in.
tapered insulation, choice c: 8 in. backs into 32 when divided by 1/4; the accepted setup gives 36 on that same base.
Option C: 12 in.
tapered insulation, choice d: 12 in. backs into 48 when divided by 1/4; the accepted setup gives 36 on that same base.
Memory Technique
Store tapered insulation with its last math move; nearby answers are usually unfinished versions of 9 in.
Reference Hint
Open Roofing Construction and Estimating, Atcheson, 1995/2022 reprint; use the index entry or section for "Tapered insulation slope calculation" to confirm that The taper changes 36 ft x 1/4 in./ft = 9 in.
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