I am bombing the Hole Punching section.

[Thetoothhurts91]

Hey everyone,

So I feel like a total failure because I purchased CDP and my score is hovering at 18 because I'm consistently failing at the hole punch portion (as in 20%-50%). I've read other threads about lines of symmetry or to picture it in your head techniques. There's also a youtube video that everyone links to:


but the original poster took it down (why?? ) I've read Barron's and the answer keys CDP tests but they don't really help me because I find myself trying to look at the answer than to arrive to it. Can anyone give a run down on how to do line of symmetry? A lot of questions I've gotten will make certain "half-holes" due to creases that open up to a new hole, or it bends diagonally so I don't know where to mark the new holes.

Sorry for the rambling, but I'm just s-t-u-c-k on this.

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[Ari Rezaei]

Check out this video:

 

[Thetoothhurts91]

I actually saw this video before and he makes it so easy. I guess it's when I actually have to apply it when I start having problems. The questions I'm getting on CDP have folds that makes half holes which opens up to a full hole and I'm not sure if I'm supposed to mark it as an X or an O. But this video was a good watch!

 

[threemileisle]

I actually saw this video before and he makes it so easy. I guess it's when I actually have to apply it when I start having problems. The questions I'm getting on CDP have folds that makes half holes which opens up to a full hole and I'm not sure if I'm supposed to mark it as an X or an O. But this video was a good watch!

There are several other videos on YT you should be able to find by searching for "line of symmetry". Think of it this way -- it doesn't matter if it's a half hole or a full hole. Mark a half hole as you would any other hole. Since you're doubling everything, the only difference is that a half hole opens up to become ONE hole, while a full hole opens up to become TWO holes. Once you get comfortable with that idea, half holes actually become easier to deal with because you know you'll no longer need to to reflect them past the first fold. Of course, if there are additional folds, just treat them as you would regular full holes.

 

[Svd2014]

You need to treat half holes as regular holes. When a half hole falls along the actual line of symmetry (where the crease is) then the hole stays there and doesn't reflect anywhere.

There's a foolproof method that gets 100% accuracy every time (which I got from the video that was taken down):
Draw out one 4x4 grid for every question, so draw 15 grids before you begin the pat section.
Always start at the right side and on your grid, draw the holes that were punched. (Treat half-holes as regular holes, there is no need to indicate if it is a half hole)
Then begin unfolding backwards until the paper is completely unfolded. The important thing is to correctly see how the paper should be unfolded with each step. (If you can't see it at first, it would even help to take a post-it and fold it according to the folds shown.)
With every unfold, reflect the holes along the crease being unfolded. which would be the line of symmetry. If there is a hole along the crease, leave that hole there. With this method you get to the unfolded paper showing where all the holes are.
Also, there is one important trick: If at any time, you end up unfolding a blank spot (where there is no hole) onto a place where you have a hole drawn on your grid, that hole gets erased because its not actually there. But if you reflect a hole onto a hole then that hole stays there. This is hard to explain, here is a question that shows a situation like that:

Starting at the right side, with the first unfold, the hole gets reflected up into the top right corner. Then the second unfold has the bottom right corner be unfolded onto the place where we drew that first hole, which means that hole gets erased. Then the next unfold reflects the top right hole into the top left corner. Finally the last unfold reflects the vertical rectangular portion onto the right side, reflecting a blank spot onto the place where we had the hole in the top right, which means that hole gets erased. You are left with only one hole in the top left corner.

 

[el_duderino]

Forgive me for going offtopic on this thread, but I just learned about the hole punching thing. This is fascinating. What's the justification behind this section of the test?

 

[emminent]

Forgive me for going offtopic on this thread, but I just learned about the hole punching thing. This is fascinating. What's the justification behind this section of the test?

Simply additional perceptual bs that dental schools want to test you to see if you can orient teeth structures correctly lol...

 

[TheDanger]

@Svd2014 Thanks for the explanation! I've been having so much trouble understanding that until now.