



 
Hi Peter, The shape of the cross section of your wall is a trapezoid. The area of a trapezoid is the average of the lengths of the parallel sides, times the distance between the parallel sides In your case that's \[\frac{36 + 24}{2}\times 42 \mbox{ square inches.}\] To calculate the volume of a section of the wall in cubic inches multiply the cross section area by the length in inches, in your case 36 inches. Cheers, 



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