Sphere Volume and Surface area/Mailing Tube Volume

[mathhurts]

Question#1- I have a Sphere and it shows 7m from the center to the outside. A, what is the volume and B, what is the surface area.
Question#2- What is the volume of a mailing tube with a diameter of 2in and a height of 40in..Thanks, Paul

Thanks, Paul

 

[Loren]

These seem to be direct application of the three formulas involved. You need to look up and memorize the formulas for (1) the volume of a sphere, (2) the surface area of a sphere, and (3) the volume of a right circular cylinder.

 

[mathhurts]

These seem to be direct application of the three formulas involved. You need to look up and memorize the formulas for (1) the volume of a sphere, (2) the surface area of a sphere, and (3) the volume of a right circular cylinder.

I am doing the best that I can. I have been out of school for 25 years and I am really struggling with this Geometry. All I was asking for was a solution so I could build on it for other related problems. It may come easy to you, but there are lots of us out here that it does not. Paul

 

[Loren]

I'll try to explain what might be an appropriate way for you to tackle the problems. Let's consider the first one.
Question#1- I have a Sphere and it shows 7m from the center to the outside. A, what is the volume?

I would google "volume of a sphere". After looking at a couple of sites, I found that the formula is \(\displaystyle V=\frac{4}{3}\pi r^3\) where r is the radius of the sphere. I also was able to find out that an approximation for pi is 3.1416. The problem tells me that the radius is 7 m, so I simply plug that value into the formula and I get \(\displaystyle V=\frac{4}{3}\pi \times 7^3\). The next step is to let my calculator compute that. I feed into my calculator 4 ÷ 3 X 3.1416 X 7 X 7 X 7 and get the answer. My wife just said "supper's ready. Good luck.

 

[stapel]

These seem to be direct application of the three formulas involved. You need to look up and memorize the formulas for (1) the volume of a sphere, (2) the surface area of a sphere, and (3) the volume of a right circular cylinder.

I have been out of school for 25 years and I am really struggling with this Geometry. All I was asking for was a solution....

There are worked examples in your text (and probably in your class notes), as well as the many site I'm sure you reviewed online. So another worked example, one which happens to end up copied into your homework, is unlikely, I'm afraid, to help with the rest of the exercises. :wink:

So try following the tutor's advice: Find and memorize the formulas. And plug the numbers you've been given into those formulas, and see where this leads. :idea:

1) You've been given the radius r of a sphere. You've been given formulas for the volume V and surface area SA of a sphere with radius r. Plug the value you were given into the formulas you were given, simplify, and write down the answers.

2) You've been given the height h and diameter d of a right cylinder. You know the relationship between the diameter d and the radius r. You've been given a formula for the volume V of a right cylinder with radius r and height h. Plug the values you were given into the formula you were given, simplify, and write down the answers.

Have fun!

Eliz.