To find the height \( h \) of the square pyramid using the Pythagorean Theorem, we need to consider the right triangle formed by the height \( h \), half the length of the base edge, and the slant height.
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Identify the elements of the triangle:
- The length of the base edge is given as 40 feet, so half of that (the distance from the center of the base to the edge of the base) is: \[ \frac{40}{2} = 20 \text{ feet} \]
- The slant height \( l \) is given as 25 feet.
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Set up the Pythagorean Theorem: We use the Pythagorean theorem in the context of the right triangle formed: \[ h^2 + 20^2 = 25^2 \]
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Calculate \( 20^2 \) and \( 25^2 \): \[ 20^2 = 400 \] \[ 25^2 = 625 \]
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Substitute these values into the equation: \[ h^2 + 400 = 625 \]
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Solve for \( h^2 \): \[ h^2 = 625 - 400 \] \[ h^2 = 225 \]
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Take the square root of both sides to find \( h \): \[ h = \sqrt{225} = 15 \text{ feet} \]
Rounding to the nearest tenth, the height \( h \) of the pyramid is \( 15.0 \) ft.
Thus, the correct response is: 15.0 ft.