Question

find the area of the triangle whose perimeter is 180cm and two of its sides are 80cm and 18cm

Answer 1

Perimeter is the sum of all three sides
And 2 of the sides are given
Therefore perimeter - sum of other 2 sides is equal to the third side.
And hence after that we can use herons formula to find the area .
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Answer 2

Hi there!!!!
First of all we will find the length of third side 
let the three sides be a,b,c
perimeter of triangle = a + b + c
180 = 80 + 18 + c
180 = 98 + c
180 - 98 = c
82 = c
hence sides of the triangle are 80,82,18 cm.
hence this triangle is scalene triangle.
therefore
we will be finding its area by using herons formula.
s ( semiperimeter ) = a + b + c / 2
s = 80 + 18 +82 / 2
s = 180 / 2
s = 90
Now finally using herons formula
whole root of s ( s-a) (s-b) (s-c)
whole square root of 90 ( 90 - 80 ) (90 - 18 ) ( 90 - 82 )
whole square root of 90 * 10 * 72 * 8
square root of 518400
= 720 sq.cm

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