Math Is Fun Forum

claudia

Guest

review

I need help with these. I looked at other forum but they all say to go to another forum. Which the forum is deleted.

4. A regular octagon rests on one of the flat sides and has a total height of 10 ft. What is the measure of one of the octagon’s sides? (1 pt.)

For #5 and #6, remember to include pictures with your work. Round answers to nearest tenth.

5. Find the area of the figure below by dividing into 3 distinct shapes. For example, you cannot use two rectangles. Use the areas of these three shapes to find the total area. (2 pts.)

6. Find the surface area and the volume of the figure below. Break your work down into three sections: Cone, Cylinder, and Sphere. Show the work for both the surface area and volume. Then find the total surface area and volume. Use 3.14 for π. R (3 pts.)

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: review

hi Claudia

Welcome to the forum.

I will help but first you need to read the advice about posting: http://www.mathisfunforum.com/viewtopic.php?id=14654

This looks like a direct copy of Compu High homework.  That company doesn't like their questions (for which they hold the copyright) being posted on the internet.  It would be better if you would ask exactly what is causing difficulties without posting the whole question.  It'll take me a while to construct a diagram for Q4 but I'll do that later today.  I cannot help with the other two, because they require a diagram which you haven't included.  One way around this is for you to describe the diagram … eg.  There' a horizontal line AB and a right angle at B to make the line BC etc etc.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: review

OK, here we go.

As the polygon is regular the 8 internal angles are equal.  There's a formula for this.  If you haven't learnt it you can get the size of one angle (BAD for example) by extending BA outside the shape.  This makes an external angle at A.  8 of these makes 360 so you can calculate one, then subtract from 180 to get BAD.

CA goes through the centre of the polygon and splits that angle in half.  So you can calculate BAC.  You know the length BC so you can use trig. to calculate BA.

From the wording it seems that Q5 is a complicated flat shape made up of shapes like rectangles and triangles whose area you can calculate.  So you need to divide it up, work out some lengths, get each area and add them up.

Q6. is similar but with a 3-D solid instead of a 2-D flat shape.  Once again you need to work out the bits and add as appropriate.

If you can,  post  diagrams or describe the diagrams in words.

Here's how I did my diagram.

(1) Get the diagram up on my laptop screen. (I googled for an octagon)

(2) Press Fn and PrtSc buttons to create a screen shot.

(3) Paste into the app Paint.  Edit as needed (I added lines and letters) and save.

(4) Log into my imgur.com account.

(5) Upload the picture.

(6) In the account pull down list select Images and choose the one I've just uploaded.

(7) Copy the BBCode into my post here.

(8) The forum software reads that Code and looks on the imgur site for the image.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob