devon studied the composite figure. he believed the surface area, in square units, could be found by…

devon studied the composite figure. he believed the surface area, in square units, could be found by simplifying the expression ( 2((9)(20)) + 2((9)(34)) + (34)(20) + 2(\frac{1}{2}(20)(24)) + 2(\frac{1}{2}(34)(26)) ). what error did devon make? he included the 34 by 20 base of the figure. he used 26 instead of 24 as the slant height of one set of lateral faces. he believed the upper part of the figure was a pyramid instead of a prism. he omitted the rectangle where the upper and lower solids join together.

devon studied the composite figure. he believed the surface area, in square units, could be found by simplifying the expression ( 2((9)(20)) + 2((9)(34)) + (34)(20) + 2(\frac{1}{2}(20)(24)) + 2(\frac{1}{2}(34)(26)) ). what error did devon make? he included the 34 by 20 base of the figure. he used 26 instead of 24 as the slant height of one set of lateral faces. he believed the upper part of the figure was a pyramid instead of a prism. he omitted the rectangle where the upper and lower solids join together.

Answer

Explanation:

Step1: Analyze the surface area formula

The formula for the surface area of a composite figure should not double - count or miss any faces. When two solids are joined, the area of the common face should be excluded from the total surface area calculation.

Step2: Check the given expression

In the given expression (2((9)(20))+2((9)(34))+(34)(20)+2(\frac{1}{2}(20)(24))+2(\frac{1}{2}(34)(26))), Devon did not account for the fact that the face where the two solids (the lower rectangular - like part and the upper part) are joined is internal and should not be included in the surface area.

Answer:

He omitted the rectangle where the upper and lower solids join together.