A new concrete pedestal has the dimensions of 3ft, 9ft, and 8ft. What is the surface area of the pedestal?

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I'm not able to solve this exact problem for you per the eNotes terms of use, but let me talk through a similar problem for you. Afterward, you should be able to use the steps shown here to solve the problem using your data.

You can determine the surface area of the pedestal—a rectangular prism—using known dimensions by first calculating the area of each of the pedestal's six faces. Keep in mind that half of the faces of a rectangular prism will always be congruent, which means we only actually need to do three different area calculations.

If our total dimensions are 2x5x6, we know that the dimensions of the individual faces are as follows:

2x5
2x6
5x6

We then multiply these to get the total area of each side:

2x5 = 10
2x6 = 12
5x6 = 30

Remember how we said there are six faces, but we have only three sets of numbers? We've calculated only the first three faces so far. The good news is that the remaining faces are congruent—all you need to do to get the final surface area is add these first three sums together and then multiply the total by 2 to compensate for the other three.

10 + 12 + 30 = 52
52 x 2 = 104

In our example, we see that the total surface area of a pedestal with the dimensions 2x5x6 comes out to 104. Repeating the steps above with your own numbers will give you the answer you're looking for.

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