To find the volume of a triangular pyramid (also known as a tetrahedron), you can use the formula:
\[ V = \frac{1}{3} \times \text{Base Area} \times \text{Height} \]
In this case, the area of the base is given as 12 square inches and the height is 7.5 inches. Plugging in the values:
\[ V = \frac{1}{3} \times 12 , \text{sq in} \times 7.5 , \text{in} \]
Calculating this step by step:
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Multiply the base area by the height: \[ 12 \times 7.5 = 90 \]
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Now, multiply by \(\frac{1}{3}\): \[ V = \frac{1}{3} \times 90 = 30 \]
Therefore, the volume of the speaker is:
\[ \boxed{30} , \text{cubic inches} \]