Perimeter of a triangle (GCSE Maths) Watch

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#1
Report Thread starter 7 years ago
#1
ABC is an isosceles triangles with AB=AC
BC=(2X-1)
AC=(X+7)
The perimiter of the triangle is 27cm
Worth out the lengh of BC.
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Mr cone
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BC = 6

edit: why neg rep me?
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#3
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(Original post by Mr cone)
BC = 6
How did you find that?
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#4
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It cant do. Because, that means x=3.75 then if you put that into formula it equals 27.5cm?
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Mr cone
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well the perimiter is equal to the addition of the lengths of the sides.
so AB+BC+AC= perimieter of ABC.
AC=AB
AC=(x+7) therefore we know that AB = (x+7) as they are the equal lengths.
BC= (2x-1)

So, as AB+BC+AC= perimieter
(x+7) + (2x-1) + (x+7) = 27
4x + 13 = 27
4x=14
x = 3.5


BC = 2x-1 = 2(3.5) -1 = 7-1 = 6
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Mr cone
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(Original post by iPad User)
It cant do. Because, that means x=3.75 then if you put that into formula it equals 27.5cm?
no it means x=3.5
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#7
Report Thread starter 7 years ago
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(Original post by Mr cone)
well the perimiter is equal to the addition of the lengths of the sides.
so AB+BC+AC= perimieter of ABC.
AC=AB
AC=(x+7) therefore we know that AB = (x+7) as they are the equal lengths.
BC= (2x-1)

So, as AB+BC+AC= perimieter
(x+7) + (2x-1) + (x+7) = 27
4x + 13 = 27
4x=14
x = 3.5


BC = 2x-1 = 2(3.5) -1 = 7-1 = 6
Thank you so much!
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Mr cone
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#8
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no problem mate
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