To calculate the capacity of the trench shaped like an upside-down rectangular pyramid, we can use the formula for the volume of a pyramid:
\[ V = \frac{1}{3} \times \text{Base Area} \times \text{Height} \]
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Calculate the base area: The base of the pyramid is the top opening (30 ft wide and 250 ft long):
\[ \text{Base Area} = \text{Width} \times \text{Length} = 30 , \text{ft} \times 250 , \text{ft} = 7500 , \text{ft}^2 \]
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Determine the height: The height of the pyramid corresponds to how deep the trench is. Here, the depth is given as 15 ft.
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Calculate the volume: Plugging the values into the volume formula:
\[ V = \frac{1}{3} \times 7500 , \text{ft}^2 \times 15 , \text{ft} \]
\[ V = \frac{1}{3} \times 112500 , \text{ft}^3 \]
\[ V = 37500 , \text{ft}^3 \]
Therefore, the capacity for the trench is 37,500 ft³.
Thus, the correct response is:
37,500 ft.³.