Heron's Formula Problem

Geometry Level 3

Find the area of a triangle with side lengths 2, 3 and 4.

Give your answer to 1 decimal place.


The answer is 2.9.

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2 solutions

Terry Yu
May 12, 2017

Heron's formula is

S = a + b + c 2 S=\dfrac{a+b+c}{2}

and the area is

A = S ( S a ) ( S b ) ( S c ) A=\sqrt{S(S-a)(S-b)(S-c)}

With a triangle sides 2, 3, and 4, S = 2 + 3 + 4 2 = 4.5 S=\frac{2+3+4}{2}=4.5 . When S = 4.5 S=4.5 , the area would be

A = 4.5 ( 4.5 2 ) ( 4.5 3 ) ( 4.5 4 ) = 4.5 2.5 1.5 0.5 = 8.4375 2.9 A=\sqrt{4.5(4.5-2)(4.5-3)(4.5-4)}=\sqrt{4.5*2.5*1.5*0.5}=\sqrt{8.4375}\approx\large\color{#3D99F6}\boxed{2.9} .

Heron's formula states that with S being equal to half of the perimeter of the triangle, and A, B, and C being the 3 sides of the triangle. Plugging in the values, we get S = 4.5, and plugging it in, we get the area is root 8.4375( the root of {4.5 * 2.5 * 1.5 * 0.5}), which is around 2.9.

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