another question to check please

silverpuma · 2011-06-27 01:49:47

Hi all, Another question from the GCSE book that I'm going through. I'm not sure the answer in the book is correct so I would be thankful if someone could look at it and confirm if I'm mistaken........again...LOL

It is question 3 a

I got B and F

The book says C and E

My understanding of congruent was that the size, angles and shape needed to be exactly the same?

Thanks

bobbym · 2011-06-27 01:52:24

Hi;

I like B and F also. C and E are not congruent.

anonimnystefy · 2011-06-27 01:54:12

I agree with bobbym.I think you are right, silverpuma.

silverpuma · 2011-06-27 02:06:23

Thanks guys on to rotational symmetry now:D I found some of the "Nets" a bit difficult I had to give 2 Nets for a Right angled Triangular prism and my 1.5 brain cells started to smoke. Eventually I got the two correct but it took my far too long, practice, practice and some more practice...........

One thing I did notice Bobbym was that there was not much on the site dealing with NETS for the more standard shapes. I have looked at the page on Platonic solids and that was helpful but a few of the not so unusual would be great. Mind though that's not in any way a criticism, I'm a very, very satisfied and thankful member.

bobbym · 2011-06-27 02:14:02

Hi silverpuma;

MIF does all that work by himself. He puts those pages together. Maybe he will someday have some free time to put more.

Bob · 2011-06-27 02:34:13

hi silverpuma

practice, practice and some more practice

If you post a solid, I'll take you through the net step by step

OR I'll find some for you to try.

Just say the word,

Bob

silverpuma · 2011-06-27 02:38:18

bobbym wrote:

Hi silverpuma;
MIF does all that work by himself. He puts those pages together. Maybe he will someday have some free time to put more.

What or who does " MIF" stand for?

I understand completely and as I said above I am truly grateful for the help so far. As we both know the web is full of maths forum and website but for me I have found the clear and well illustrated modules here the best for my learning. I have looked for a donate page/paypal but can't see anything as I'd like to gift the owner of the site the price of Starbucks as a small token of appreciation. Is there away to do that Bobbym?

anonimnystefy · 2011-06-27 02:42:36

MIF stands for MathIsFun which is the name of the administrator of the forum and the name of the forum itself.

bobbym · 2011-06-27 02:43:24

Hi;

Sorry for the abbreviation, he is none other than MathsIsFun, the administrator.

Is there away to do that Bobbym?

I will direct him to this thread. He can answer your questions. Is that satisfactory?

silverpuma · 2011-06-27 02:53:30

bobbym wrote:

Hi;
Sorry for the abbreviation, he is none other than MathsIsFun, the administrator.
Is there away to do that Bobbym?
I will direct him to this thread. He can answer your questions. Is that satisfactory?

Thanks..........

bobbym · 2011-06-27 02:55:10

Hi silverpuma;

Bob Bundy has left you a message in post #6.

silverpuma · 2011-06-27 03:12:00

bobbym wrote:

Hi silverpuma;
Bob Bundy has left you a message in post #6.

Thanks Bobbym for spotting that for me. In the flurry of posts there I missed that one.

Right Bob, first thanks for the offer. What I'm looking for is clues or tips I can use on most nets. For example I saw on Cube nets as long as I had one face on each side of the 4 faces in a row that made up the cube spine it would work. I completed a few triangular prisms and they were fairly straightforward but for some reason I found the right angles triangular prism a bit confusing especially having to show two different nets for the one shape. Am I correct in thinking you can one have 2 Nets for any right angles triangular prism?

A few shapes but I don't want to be a nuisance Bob so feel free to say sorry can't help at this time...........

I can get the first Net ok its the second one I get a bit confused with.

Last edited by silverpuma (2011-06-27 03:13:13)

Bob · 2011-06-27 04:13:56

hi silverpuma,

One thing that I think will help is to get some card and try making them. You could always work together with your ten year old, then you've got an excuse if anyone else wonders what you're up to at your age.

To make a solid from a net you need to add 'tabs'; ie. extra bits to the edges for glueing. Not every edge will need its own tab, so it's a good exercise, just working out which ones. Or do it the lazy way and put tabs on all edges, then cut off the ones you didn't need.

When you talked about the cube you referred to the 'spine' of the solid. That's a good start. All prisms have an end shape; for a cube the end shape is a square; and for all the triangular prisms it's a triangle. Then the ends have to be joined by rectangles.

The rectangles will all be as long as the 'spine' and their widths will be fixed by the lengths of the sides of the end shape.

So for the last prism in your examples I started with three rectangles in the middle. They are all 8 cm long. One has a width of 2.5 cm; one is 6 cm; and the last is 6.5 cm wide.

Imagine making that in card and 'scoring' the lines to make it fold nicely. Fold it round and you've got a tube (bit like a distorted Toblerone tube). If you wanted to make this, one 8 cm long tab along either the 2.5 x 8 rectangle or the 6.5 x 8 rectangle would allow you to stick it.

Then you need the ends. I joined one triangle at each end using the 6 cm edge. If making it you'd need tabs on the 6.5 and 2.5 edges of the rectangles so you could fold the end in and stick it. Same at the far end.

You'll know if it's right because your finished solid will look like the picture in the question.

So, to summarise, make the tube, then add the ends.

There will always be other ways of doing it, because you could join the triangles along the 6.5 edge or the 2.5 edge, or one of each.

You can also have more complicated nets that still work. After all; it just has to be 3 rectangles and 2 triangles of the right sizes, that fold up to make the solid. That's the ultimate test. Does it make the solid?

When you've thought about this one, I've found a GCSE question that will lead us to lesson 2.

Post back,

Bob

Last edited by Bob (2011-06-27 04:16:32)

Bob · 2011-06-27 04:35:30

hi again,

Thought I'd have a go at a 'more complicated' net for the same solid. But I ran out of space on screen to fit it all in. So I've shrunk it a bit to fit it in. Some loss of picture quality.

Notice it has the same 3 rectangles and 2 triangles, still joined along 'matching' edges, but in an unusual position. Any answer will get you the marks so you wouldn't have to do it like this.

Bob

Last edited by Bob (2011-06-27 04:41:57)

silverpuma · 2011-06-27 13:39:10

still joined along 'matching' edges, but in an unusual position

Aaaah..........This was the phrase that jumped out at me. I would never have seen that "unusual" Net so its opened my eyes up to how I look at these problems now. And you're explanation was crystal clear. I've tried a few more and the light is beginning to dawn in that void between my ears;) Seriously though Bob thank you for this help, its appreciated .

Bob · 2011-06-27 19:49:15

hi silverpuma,

I'm very happy to help.

See how you get on with the question below. Post back and I'll give you some more help.

Bob

silverpuma · 2011-06-28 01:59:31

Bob, The ansewer to the question is:

A = 8

B = C

I did out the nets for the 4 shapes for practice using Paint but my drawing skills needs some work

anonimnystefy · 2011-06-28 02:03:13

hi silverpuma

i think your answers are correct.The same holds for the nets.

Bob · 2011-06-28 02:57:08

hi silverpuma,

Yes, all correct! Well done!

Supplementary question on these solids:

Definition of a Prism:

A solid object that has two identical ends and all flat sides.

The cross section is the same all along its length.

Definition of a Pyramid:

The base is a polygon (a straight-sided flat shape)

The sides are triangles which meet at the top (the apex).

So for each of the solids in the question, (i) say what it's name is and (ii) say if it's a prism, a pyramid, or neither.

Bob

Last edited by Bob (2011-06-28 02:57:56)

silverpuma · 2011-06-28 20:29:07

bob bundy wrote:

hi silverpuma,
Yes, all correct! Well done!
Supplementary question on these solids:
Definition of a Prism:
A solid object that has two identical ends and all flat sides.
The cross section is the same all along its length.
Definition of a Pyramid:
The base is a polygon (a straight-sided flat shape)
The sides are triangles which meet at the top (the apex).
So for each of the solids in the question, (i) say what it's name is and (ii) say if it's a prism, a pyramid, or neither.
Bob

Bob, Iassume you are talking about the 4 shapes in the images you posted above?

A = Cube / Prism

B = Cylinder / Not a Prism

C = Square based Pyramid / Not a Prism

D = Triangular Prism / Prism

This has been really helpful Bob and I think I have a resonable grasp for now. I took your advice and cut out some paper nets or cubes, rectangles and pryrimds etc and this made things very clear for me. Now its decimals for lunch LOL

anonimnystefy · 2011-06-29 01:48:25

hi silverpuma

i think those are correct answers.

Bob · 2011-06-29 06:33:05

hi silverpuma,

Sorry about the late reply. I've been without my broadband connection all day. Just 'borrowed' another wi fi. (legally of course!!)

Opinions differ about whether a cylinder is also a prism (limiting case of a polygon with infinite sides) and whether a cone is a pyramid.

I used the MIF definitions.

When you get to the formulas for the volume of these solids the cylinder and cone share the same type of formula as the prisms and pyramids respectively. But I'm jumping ahead many lessons I suspect.

Yes, all correct. Glad you feel you are getting the hang of it.

Want one last net?

See below.

Bob

Last edited by Bob (2011-06-29 06:37:14)

silverpuma · 2011-06-30 14:30:10

bob bundy wrote:

hi silverpuma,
Sorry about the late reply. I've been without my broadband connection all day. Just 'borrowed' another wi fi. (legally of course!!)
Opinions differ about whether a cylinder is also a prism (limiting case of a polygon with infinite sides) and whether a cone is a pyramid.
I used the MIF definitions.
When you get to the formulas for the volume of these solids the cylinder and cone share the same type of formula as the prisms and pyramids respectively. But I'm jumping ahead many lessons I suspect.
Yes, all correct. Glad you feel you are getting the hang of it.
Want one last net?
See below.
Bob

Hi Bob, Image attached. Just wondering as this according to MIF is not a prism what would it be called..............A hexagonal Pyramid ? Thanks again for the nets help its been appreciated

anonimnystefy · 2011-06-30 21:23:27

correct.yes actually that is what it is called.

silverpuma · 2011-06-30 21:42:58

anonimnystefy wrote:

correct.yes actually that is what it is called.

Thanks anonimnystefy no major blips this time LOL

Math Is Fun Forum

#1 2011-06-27 01:49:47

another question to check please

#2 2011-06-27 01:52:24

Re: another question to check please

#3 2011-06-27 01:54:12

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#4 2011-06-27 02:06:23

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#5 2011-06-27 02:14:02

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#6 2011-06-27 02:34:13

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#7 2011-06-27 02:38:18

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#8 2011-06-27 02:42:36

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#9 2011-06-27 02:43:24

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#12 2011-06-27 03:12:00

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#13 2011-06-27 04:13:56

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#14 2011-06-27 04:35:30

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#15 2011-06-27 13:39:10

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#16 2011-06-27 19:49:15

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#17 2011-06-28 01:59:31

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#18 2011-06-28 02:03:13

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#19 2011-06-28 02:57:08

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#20 2011-06-28 20:29:07

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#21 2011-06-29 01:48:25

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#22 2011-06-29 06:33:05

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#24 2011-06-30 21:23:27

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#25 2011-06-30 21:42:58

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