Math Is Fun Forum

silverpuma

Member

Registered: 2011-06-19

Posts: 80

Polygon angles question to check

Hi all,  I have another question to check where I can't get the books answer.

Question:

Five of the in a hexagon are 130, 102, 105, 97 and 103.  Find the size of the sixth angle.

I did the following:

180 x (n-2)

180 x 4 = 720

720 - 130 + 102 + 105 + 97 + 103

720 - 537

183

Book says 173

I could be doing the same mistake over and over and need a fresh pair of eyes to see my daft moment LOL

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“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.”  ―  Winston Churchill

soroban

Member

Registered: 2007-03-09

Posts: 452

Re: Polygon angles question to check

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silverpuma

Member

Registered: 2011-06-19

Posts: 80

Re: Polygon angles question to check

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No I checked this very carefully before I sent it in to the forum as I thougth initially I have perhaps taken down the wrong numbers myself in my own working out.  They are 100% correct.  So the mistake is in the book, I'm glad I thought I was just being really daft..................it happens................   Thanks for taking the time to help...........

Last edited by silverpuma (2011-07-12 09:27:16)

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“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.”  ―  Winston Churchill

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Polygon angles question to check

Hi silverpuma;

When in doubt it pays to draw the shape in question. Serves as a good check and gives you confidence in the result.

The irregular hexagon was drawn freehand so the angles are not exact. But you can see angle A is much closer to 183°

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

silverpuma

Member

Registered: 2011-06-19

Posts: 80

Re: Polygon angles question to check

Good point Bobbym.  I had not thought about doing that and it makes sense, I like it!!!

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“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.”  ―  Winston Churchill

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Polygon angles question to check

Hi;

Mathematics is the only field left where you do not need to blindly trust the voice of authority. You can check answers for yourself. Prove it to yourself. The book answer is clearly wrong!

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.