The tread depth of the stairway is 10.6 according to the riser tread formula.
According to the statement
we have to find the tread depth of the stairway.
So, For this purpose, we know that the
The riser tread formula is the typical interior stair dimension is calculated as the formula, riser (R)+ tread (T) = 17 inches minimum, or 18 inches maximum, not including the nosing. The nosing is the projecting edge of a tread.
Here, The given information is:
Total rise = 9 feet
Now, 1 foot = 12 inch
So, 9 x 12 inches = 108 inches
A riser height between 7 and 8 inches,
i.e., 8 ≤ h ≤ 7
Total riser = xh ...(1)
where x is the number of steps and h is the riser's height.
From equation (1),
x = Total riser ÷ h
Total riser = 108
h = 8 ≤ h ≤ 7
Thus,
x = 108/8 ≤ h ≤ 108/7
x = 14 ≤ h ≤ 15 ....(2)
Since the number of steps (x) is an odd number,
So, x = 15 [from equation (2)] (.°. 14 is not an odd number)
Also, from equation (1),
h = total riser/x
h = 108/x = 108/15 = 7.2 [it's between 7 and 8]
from riser-tread formula,
2h + d = 25
d = 25 - 2h
d = 25 - 2(7.2)
d = 25 - 14.4
d = 10.6
Thus, The answer is 10.6.
So, The tread depth of the stairway is 10.6 according to the riser tread formula.
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