Question

find the length of the third side of a triangle whose two sides are 4cm 5cm and the perimeter is 18 cm

Answer 1

Hey mate here is the answer...
The perimeter of you triangle= sum of all sides
Therefore, let the third side of the triangle be 'x'.
Then, x+4+5 = 18
x+9 = 18
x = 18 - 9
x = 9
Therefore the length of the third side of the triangle is 9 cm.

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Answer 2

Here is your answer-

let,
In ∆ABC,
AB = 4cm, BC = 5cm ,AC = ?
Perimeter of triangle= 18cm

Perimeter of triangle = AB + BC + AC
18 = 4 + 5 + AC
AC = 18 - 9
AC = 9cm

Therefore, the length of third side of triangle is 9cm

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