Can you solve it?

imported_lev

Junior Member
Apr 24, 2004
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the top line on the bottom figure is not straight. in fact if you drew a straight line from each of the end points you would get a trianle with the same area of the square divided by two. This is a little hard to see since the borders of each shape are comparatively thick.

Notice that the top figure is not a trangle. And if you drew a line connecting each of the end points of the top line of the top figure, you would get a trianle. And the area of the triangle is the other half of the area for the square.
 

ss284

Diamond Member
Oct 9, 1999
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Take a look at the dimensions (base x height) of the "triangle" (5 x 13). Then take a look at the dimensions of the two triangles used to make the hypotenuse of the triangle. Realize that they do not match the dimensions of the original triangle (2 x 5) and (3 x 8). They are close, tricking your mind into thinking that the angle of the hypotenuse in respect to the base is the same, when they are in fact not. Both of the figures (ignoring the little gap in the second) you are looking at aren't triangles, they are infact 4 sided shapes(there is an edge where both triangles touch). That gives you the illusion they are the same shape, when they arent. Add up the area of each of the separate objects using basic math. You have the same area. This is just the illusion of a triangle, when it actually isnt, thus 1/2(b*h) cant be used to accurately calculate the area.

-Steve
 

Juice Box

Diamond Member
Nov 7, 2003
9,615
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oh wow, i didnt even see that! Now i understand, except why is the top figure not technically a triangle? because the bottom line isint really straight?
 

ss284

Diamond Member
Oct 9, 1999
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Originally posted by: digitalsnare
oh wow, i didnt even see that! Now i understand, except why is the top figure not technically a triangle? because the bottom line isint really straight?

Because the hypotenuse isnt straight.
 

ss284

Diamond Member
Oct 9, 1999
3,534
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Im too lazy to think any more, but I would think the first triangle without the extra gap has a concave hypotenuse, while the second triangle has a convex hypotenuse. I could be wrong since im hungry.


Lunch time, cya.

-Steve
 

PacFu

Member
Jul 1, 2004
158
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no no no, its has nothing to do with angles...

the question here is area and volume, not angles.

Ok, forget the fact there are the red and green triangle, lets just concentrate on the middle 2 shapes and the rectangle it forms. Simple Tetris math here :D

Area = L x W

On the top triangle (lets call it TriA) the area of the rectangle is 5x3=15
The bottom, TriB, the rectangle area is 8x2=16

There is where the hole comes from.

Why? As a whole you are dealing with volume, not area. I'm too tired to figure hypotenuses.
 

ss284

Diamond Member
Oct 9, 1999
3,534
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Originally posted by: PacFu
no no no, its has nothing to do with angles...

the question here is area and volume, not angles.

Ok, forget the fact there are the red and green triangle, lets just concentrate on the middle 2 shapes and the rectangle it forms. Simple Tetris math here :D

Area = L x W

On the top triangle (lets call it TriA) the area of the rectangle is 5x3=15
The bottom, TriB, the rectangle area is 8x2=16

There is where the hole comes from.

Why? As a whole you are dealing with volume, not area. I'm too tired to figure hypotenuses.

Maybe you should look a little closely, as you dont seem to understand the significance of the puzzle. It actually has everything to do with angles, especially when dealing with triangles. If the triangles arent similar to each other as well as the larger triangle, then the whole shape isnt a triangle.


-Steve
 

ss284

Diamond Member
Oct 9, 1999
3,534
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Originally posted by: PacFu
no no no, its has nothing to do with angles...

the question here is area and volume, not angles.

Ok, forget the fact there are the red and green triangle, lets just concentrate on the middle 2 shapes and the rectangle it forms. Simple Tetris math here :D

Area = L x W

On the top triangle (lets call it TriA) the area of the rectangle is 5x3=15
The bottom, TriB, the rectangle area is 8x2=16

There is where the hole comes from.

Why? As a whole you are dealing with volume, not area. I'm too tired to figure hypotenuses.

BTW, volume is a measurement of 3 dimensions. Area is a measure of 2 dimensions. Unless I'm blind, I dont see that extra 3rd dimension, since triangles are 2 dimensional objects, as are all the shapes in this problem.

-Steve
 

silverpig

Lifer
Jul 29, 2001
27,703
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Hold a piece of paper along the hypotenuses (sp?) of the two large triangles to see why.
 

Peter

Elite Member
Oct 15, 1999
9,640
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... and here's another one of the "problems" that recur every month or so.

Without looking: 2/5 does not equal 3/8. The big shape is not a triangle.
 

wacki

Senior member
Oct 30, 2001
881
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Originally posted by: Peter
... and here's another one of the "problems" that recur every month or so.

Without looking: 2/5 does not equal 3/8. The big shape is not a triangle.

Yup. Noobs, gotta love em.
 

jay75

Member
Jun 1, 2003
111
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the top triangle has a concave hypotenuse(pushed inwards), and the bottom triangle has a convex hypotenuse(pushed outwards). the top vertex of the green triangle in the bottom picture, is well above the point it should be in, had that same triangle been put in the top picture. and the left most vertex of the green triangle in the top picture, does not correspond with where the line cuts in the bottom picture. the convex triangle(if you can call it that now!) minus the area of the concave triangle is equal to the "hole" in the second triangle. but it's a nice trick anyhow!
 

Peter

Elite Member
Oct 15, 1999
9,640
1
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If it's not straight it's not a hypotenuse. But you're correct in that the loooong razor thin difference between the inward and outward bent ramps is exactly one square.
 

Geniere

Senior member
Sep 3, 2002
336
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I first saw this "puzzle" at least 10 years ago. It's as crooked now as it was then.
 

Cogman

Lifer
Sep 19, 2000
10,286
145
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yep, this is a Repost, and yes IMO it is pretty easy to see that there is a bump in the hypotenuse
 

Mday

Lifer
Oct 14, 1999
18,647
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yeah, i couldnt get it the first time i saw it many years ago... its still not a triangle =D