What is the area of a triangle with side lengths 18, 24, and 30?
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Good observation that the triangle is similar to a favorite 3 − 4 − 5 right triangle.
We can calculate that the area of the 3 − 4 − 5 triangle is 6. What would the area of this similar triangle be?
A² = s(s-a)(s-b)(s-c) A²= (18+24+30)/2 (s-a)(s-b)(s-c) A²= 33,5 (33,5-18)(33,5-24)(33,5-30) A² = 33,5 . 15,5 . 9,5 . 3,5 A²= 46656 A= 216
Since the lengths of the triangle have a GCF not equal to 1 then we can reduce it by the principle of similar triangles, this would give us the "simplest" lengths of ( 9 , 1 2 , 1 5 ) . There are several approaches you can work on, here are some:
(1) Since the lengths satisfy the pythagorean relation, a 2 + b 2 = c 2 , we can proceed to A = ( 1 / 2 ) ( b h ) with the two shorter sides be base or height.
A = ( 1 / 2 ) ( 9 ) ( 1 2 ) A = 5 4 and since the side ratio of the original triangle and the simplest triangle, the ratios of their areas is equal to its square, thus,
A = 5 4 ( 4 ) = 2 1 6
(2) Since we were given lengths of sides of the triangle, we can use Heron's Formula: A = ( s ) ( s − a ) ( s − b ) ( s − c ) where s is the semi perimeter of the triangle.
s = ( 1 / 2 ) ( 1 8 + 2 4 + 3 0 )
s = 9 + 1 2 + 1 5
s = 3 6
Thus,
A = ( 3 6 ) ( 3 6 − 1 8 ) ( 3 6 − 2 4 ) ( 3 6 − 3 0 )
A = 6 6
A = 2 1 6
Which agrees with (1).
I committed some errors, on ( 9 , 1 2 , 1 5 ) sorry about that.
a=18,b=24,c=30 Area=Sqrt[s(s-a)(s-b)(s-c) where 2s=a+b+c s=36, s-a=18, s-b=12, s-c=6 Area= sqrt[36x18x12x6]= sqrt[6x6x6x3x6x2x6]=6x6x6=216
we can do it by either the herons formula or the simple formula... both ways, the area is 216
Clearly 2 4 2 + 1 8 2 = 3 0 2
Hence it is a Right-angled Triangle
So, Area = 2 1 × b a s e × h e i g h t = 2 1 × 1 8 × 2 4 = 2 1 6
18 , 24 , 30 is a triangle , then by divide all by 6 we get 3 , 4 , 5 as we know these lengths belong to Right-angled triangle , then area of that triangle will be ( 1/2 * 24 ) * 18 = 216 answer is = 216
by heorn's formula :_ [s(s-a)(s-b)(s-c)]^1/2 we get
semi perimeter (S):_ a+b+c/2 (where a,b,c are lengths of sides of triangle)
30+18+24/2= 36
by the heron's formula :- put the value of s 'a'b'c
area of triangle is :_ [36(36-18)(36-24)(36-30)]^1/2 = 216
there are 3 sides given in the triangle so we will find the area by Heron's Formula . Let a=18 , b=24 , c=30, S = a+b+c / 2 = 18+24+30 / 2 = 36 Area = \sqrt{s(s-a)(s-b)(s-c)} =\sqrt{36(36-18)(36-24)(36-30)} =\sqrt{36 * 18 * 12 * 6} =\sqrt{46656} =216
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From the side lengths 18, 24, and 30, we can see that it forms the ratio of 3:4:5
Hence, we can deduce that this is a right angled triangle, with 18 and 24 forming the right angle. To find the area, we do (18*24)/2=216 and we get the answer.