line puzzle

[aslbow]

Draw the shape of a cruciform, ie; a cross such as the one on a red cross symbol, that is equal on each side. Now, divide the shape into seven regions using only two straight lines.

[Zag]

Hi aslbow! Welcome to the Grey Labyrinth! We're always glad to have new people with original (or, at least, very obscure) puzzles. Is this your own? It's ok if it is not, but you should give credit if you know the original author, or at least declare that you didn't create it. If you did create it, then more power to you!

This seems like such a basic puzzle that it should be a chestnut, but I have to admit that I don't know the answer, and a few minutes of scribbling didn't get me there. I finally gave up and tried to google the answer. It looks like this author couldn't do any better than the obvious six pieces.

Do you move the pieces after the first cut, or fold the paper? (It's pretty easy with either of those tricks.) Or did I just miss something that's right in front of my nose? (It wouldn't be the first time.)

[aslbow]

it cannot be bent or cut. the lines must stay inside the shape. it is not mine and i dont know the author.my genius son sent it to me. he is an academic graduate at age 19 and is a dual physics major. He says it took him a few days to figure out. good luck, and no, i dont have the answer yet either. lol.

[gftt*]

Not possible to get 7. Each line only intersects the shape twice at most, and the two lines can only intersect each other once. 1 original shape + 2 + 2 + 1 = 6.

[3iff]

I agree. 6 is easy to get but there are just not enough lines available to get 7.

[L'lanmal]

I'm thinking the parts of the "shape" are meant to include those originally unbounded, but become bounded with addition of lines. (That is, the lines are additions to the figure, and not cuts of it.)
In this case, there are several ways to get 8 bounded regions, and taking one to a degenerate case gets you 7. Two parallel diagonal lines which each form 4 intersections, for instance.

[aslbow]

I read your posts but have no idea what u mean by two parallel lines making up 4 intersections. I am not the college kid, i'm the dumb dad. lol. please explain in Earth language.

[Chuck]

Maybe the seven doesn't mean seven regions but that each region should be shaped like a seven.

[3iff]

That sort of cheat-question would not be worthy of a genius son...

It's no hassle to shape them as an "L" though or even as a 7 if you connect opposite corners...

[referee]

He means like counting the small triangles that are actually outside the cross in the link Zag posted in the first reply.

To get seven, you just make one of the lines pass trough the inside point of the cross, and it won't create an outside triangle.
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[aslbow]

ahhh...i see. I will forward that solution to him and see if it flies. I will let you know. Thanks!

[Zag]

[aslbow]

Zag, i think your talking about the matchstick puzzle that has all the stick ends in the middle together. Then move one to make a square. The answer is to move the top one up one stick width to leave a squre in the space vacated.

[Zag]

No, I put the answer in my post using spoiler tags in the post. They cause the text to be in Grey on Grey. However, you can see it if you select it (by hitting Ctrl-A, for instance).