# Backing: Why a Rectangle is bigger than a Square

• 07-19-2012, 06:07 PM
SuzzyQ
Backing: Why a Rectangle is bigger than a Square
Twists your minds but it makes sense!

https://i.chzbgr.com/completestore/1...QjIGjVgaQ2.gif
• 07-19-2012, 06:15 PM
auntpiggylpn
Yes, it did twist my mind and No, it doesn't make sense to me!!!
• 07-19-2012, 06:17 PM
Ditter43
That is one of THOSE things!!!!!AArrrggg
• 07-19-2012, 07:11 PM
Latrinka
Mind boggling!
• 07-19-2012, 08:17 PM
Rubesgirl
I'm math challenged on my good days! This seems totally improbable. If you take the square and reposition the parts without adding on, it should be the same no matter what... right?
• 07-20-2012, 03:40 AM
QuiltnNan
Quote:

Originally Posted by Rubesgirl
I'm math challenged on my good days! This seems totally improbable. If you take the square and reposition the parts without adding on, it should be the same no matter what... right?

ditto. doesn't make sense to me either
• 07-20-2012, 08:26 AM
raynhamquilter
WHAT?! I don't understand it.
• 07-20-2012, 08:44 AM
mom-6
Makes my brain hurt! LOL!
• 07-20-2012, 02:02 PM
ptquilts
the solution, courtesy of Google (of course)

actually these fit in the category of optical illusions

In the first diagram, the red and blue triangle have different angles. W/o using trig, you can see the slope of the red triangle is portrayed as 2/5, while the blue triangle is portrayed as 3/8. In the picture with emboldened lines, the eye can't see the difference between .4 and .375, but it is there. If the angles were the same, the blue triangle would intersect halfway between the first 2 graph points, and in the second portion of that diagram, the blue shouldn't actually cover the 8 spaces spanned by the green and light blue figures. The hole comes from the fact that you cannot calculate the total area of the first triangle as (13*5)/2=32.5, because in actuality, keeping the angles to be the same, it's (12.5*5)/2=31.25. In the second picture, to keep the angles the same, you would have to add the areas because the blue wouldn't complete a triangle, so blue=7.5*3/2=11.25, green=8,lblue=7,red=2*5/2=5, total is magically 31.25

The second diagram is the same principal, the angles that are being matched between the 2 symetrical orange pieces and the 2 symetrical green pieces don't match. Again, .375 vs .4, the unseen gap is what equates to the differing apparent areas.
• 07-20-2012, 04:09 PM
DogHouseMom
PTQuilts - thanks for the "translation"

I actually see it now ... look close at the red triangle and the green triangle - especially when matched to each other in the rectangle - and you will see that where the two meet to make a completed square of both red and green ... it's not a true square.
• 07-21-2012, 06:31 AM
willferg
I showed this to my daughter and asked her to figure it out for me. She cut it out in graph paper, cut the pieces, and then showed me how when she went to reassemble them, they didn't truly fit right, despite what the video clip shows. That accounted for the extra square. She said the slopes of the boxes didn't match and that's why they didn't fit together right.

I wouldn't have thought to do that...
• 07-21-2012, 09:10 AM
sherryl1
I don't think I am smart enough to understand that.Oh well.
• 07-21-2012, 01:21 PM
caspharm
It looks similar to the way one quilt teacher ( John Flynn) was showing how to make a quilt backing by cutting the fabric at an angle and sliding it.
• 07-23-2012, 05:26 AM
gmcsewer
Maybe this explains why our quilts don't always fit together like they should!