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?

Question

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?

👇

2 answers
(click or scroll down)

👇

Answer 1

Alex answered
7 years ago

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.

Answer 2

Explain Bot answered
11 months ago

To solve the problem properly, you need to follow the correct order of operations and use the well-known formula for calculating the volume of a cylinder, which is V = πr^2h.

Let's break down the calculation step by step:

1. The formula for the volume of a cylinder is V = πr^2h, where r represents the radius of the base and h represents the height.

2. In your case, the radius (r) is given as 4 inches, and the height (h) is given as 9 inches.

3. To find the volume, substitute the values into the formula: V = π(4in)^2(9in).

4. Begin by squaring the radius: V = π(16in^2)(9in).

5. Simplify the multiplication: V = π(144in^3).

6. Finally, the answer should be written as 144πin^3, not 452.

So, the correct answer is indeed 144πin^3. If your calculator is giving you a different answer, it is most likely due to incorrect input or an error in using parentheses or the π symbol on the calculator. Please double-check your calculations and make sure you are using the correct values and symbols in the calculation.