We assume the 1/8 scale factor is the ratio of the linear dimensions of the smaller of the prisms to the larger. The ratio of areas will be the square of the ratio of the linear dimensions.
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The ratio of areas will be ...
smaller area / larger area = (scale factor)²
smaller area = (larger area)×(scale factor)² . . . multiply by the denominator
smaller area = (740 ft²) × (1/8)² = 11.5625 ft² . . . use given values
The surface area of the smaller prism is about 11.6 square feet.
