You're doing it right. Exact answer just means to keep your answer in symbolic form-- keep your constants.
pi * 4^2 * 9 = 144pi (exact)
If we wanted the approximate answer, we could substitute pi = 3.14, and then you get 452.
I am doing volume and surface areas of 3D figures, and am running into the problem of having to give the exact answers as well as approximate answers. The approximate answers I don't have a problem with but the exact answers are requiring me to get the solution of a problem like: Pi x (4in)^2 x 9in. I type it into my calculator and get 452. but the homework is the correct answer is 144pi in^3. I just don't understand what I am missing?
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