To find the surface area of the figure shown, Mia found the surface area of the two triangular prisms and the rectangular prism.
From this, Mia subtracted 6 ft2. Did Mia make an error? Mia should have subtracted 16 square feet. Mia needs to subtract another 6 square feet. Mia must calculate each triangle separately. There is no error—Mia is correct.
