To find the capacity of the trench in the shape of an upside-down rectangular pyramid, we can use the formula for the volume of a rectangular pyramid:
\[ V = \frac{1}{3} \times \text{Base Area} \times \text{Height} \]
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Calculate the Base Area:
- The base area can be calculated by multiplying the width and the length of the top opening. \[ \text{Base Area} = \text{Width} \times \text{Length} = 30 , \text{ft} \times 250 , \text{ft} = 7500 , \text{ft}^2 \]
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Calculate the Height (Depth):
- The height of the pyramid (depth of the trench) is given as 15 ft.
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Calculate the Volume: \[ V = \frac{1}{3} \times 7500 , \text{ft}^2 \times 15 , \text{ft} \] \[ V = \frac{1}{3} \times 112500 , \text{ft}^3 = 37500 , \text{ft}^3 \]
So, the capacity for this trench is:
\[ \boxed{37,500 , \text{ft}^3} \]