Using the unit-length method, calculate the total theoretical length of a rafter if the unit rise is 18″, the span is 8′, and the total run is 4′.
A. 86.52″
B. 173.04″
C. 21.63″
D. 64.89″
Is it C?
To calculate the total theoretical length of a rafter using the unit-length method, you need to determine the unit run and then multiply it by the total run.
The unit run can be calculated by dividing the total run by the span. In this case, the total run is 4' and the span is 8'. Therefore, the unit run is 4' / 8' = 0.5'.
Once you have the unit run, you can multiply it by the total run to get the total theoretical length of the rafter. In this case, the total run is 4' and the unit run is 0.5'. Thus, the total length of the rafter is 4' * 0.5' = 2'.
Converting the total length from feet to inches by multiplying it by 12 (since there are 12 inches in a foot), the total length becomes 2' * 12 = 24"
Since the total length of the rafter is 24", the correct answer is not C.
Therefore, the correct answer is not C.