GCSE Maths Intermediate Interior/Exterior angels Watch

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fivebyfive
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#1
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#1
Hi,

I am doing a question on interior/exterior angels i can solve it but only via trial and error.

"Find the value of X in the following Polygon" Interior angels shown as 2x, x+20, 2x+5, 85.

Answer= x=50. 180-100=80; 180-70=110; 180-105= 75, 180-85=95

80+110+75+95=360 (exterior angles sum). Therefore x 50 is correct, as stated though this answer was only obtained via trial and error.

Is there a easier way then trial or error or is this the required method for intermediate level?

Thanks
5by5
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Speleo
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2x + x+20 + 2x+5 + 85 = 360 (interior angles add up to 360)

5x + 110 = 360 (simplify)

5x = 250 (-110 from both sides)

x= 50
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fivebyfive
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(Original post by Speleo)
2x + x+20 + 2x+5 + 85 = 360 (interior angles add up to 360)

5x + 110 = 360 (simplify)

5x = 250 (-110 from both sides)

x= 50
Thanks for that.
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Speleo
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No problem
You can pm me if you're stuck on any more GCSE questions if you like.
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allanonthedruid
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Have a look at the revision notes at www.mathsangel.co.uk - they're free I think.
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