Hole Punching Question

[krzeduckii]

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Can anyone explain why C is the correct answer? I tried the tic tac toe method but couldn't get it

http://www.datqvault.com/include/images/dat_questions/pat/holes/qa83.jpg

 

[sskater]

1st step (For me): Line of Symmetry! (LOS)
I immediately look at the first LOS and eliminate B! As it does not reflect across the diagonal axis.

2nd step: Count the number of "folds" so we know how many holes to expect.
1st Fold: 2
2nd Fold: 4 on left half, 2 still on right half
3rd Fold: 4 on the upper triangle, still 4 on the lower half uncovered by the triangle.

So now I look at the answers, which one has4 Holes?, I see there's B and C, but we've already eliminated B! So the Answer is C.

With more exposure, you'll be able to mentally visually/fold these in your head. Practice with some square post-its if you want, DO NOT use regular notebook/printer paper as its not SQUARE.

EDIT: I see that you might be tempted to pick something with holes on top. But notice when we unfold from B-->A, the upper border of the square is empty in A, so there will be no hole "punched" there.

 

[Datooth]

It works with the tic-tac toe method. You should double check that you've done it correctly. Don't forget that you need to remove the initial set of marks due to the paper collapsing onto them.

 

[wolfchild007]

don't mark the top two punches because you have to fold the trapezoid down to make the triangle(first fold). You instead mark those two punches on the bottom middle of the triangle (fist fold)

 

[krzeduckii]

Thanks! So just to clarify, one fold counts as 2 holes?

 

[sskater]

Thanks! So just to clarify, one fold counts as 2 holes?

Yes, but keep track of the number of folds.

I tend not to use this method because you'll start being able to effectively use the tictactoe method.

 

[krzeduckii]

It works with the tic-tac toe method. You should double check that you've done it correctly. Don't forget that you need to remove the initial set of marks due to the paper collapsing onto them.

Oh no that's exactly what I did wrong! Can you please explain more about removing the initial marks due to the paper collapsing onto them? I'm confused on that part lol

 

[sskater]

Oh no that's exactly what I did wrong! Can you please explain more about removing the initial marks due to the paper collapsing onto them? I'm confused on that part lol

What @Datooth means is when in the First picture, when you unfold back to its "original square shape", we see an "unpunched" area collapsing on the area where you have your initial set of marks, rendering them "invisible". So there are no more marks there and your other two marks get reflected on the axis of symmetry!

 

[Datooth]

Oh no that's exactly what I did wrong! Can you please explain more about removing the initial marks due to the paper collapsing onto them? I'm confused on that part lol

https://www.youtube.com/watch?v=7ud0ZX0eEFA

Check around 9:50. You'll notice that he'll blot out a few X's. His explanation is probably easier to understand.

What @Datooth means is when in the First picture, when you unfold back to its "original square shape", we see an "unpunched" area collapsing on the area where you have your initial set of marks, rendering them "invisible". So there are no more marks there and your other two marks get reflected on the axis of symmetry!

Exactly.

 

[krzeduckii]

Wow that video helped a lot. Thanks for the help guys 🙂