Find area of triangle [Heron's Formula]

• Jan 11th 2009, 05:03 PM
Intrusion
Find area of triangle [Heron's Formula]
I thought I knew how to do this, but I keep getting the incorrect answer. Can someone help me out? Thanks in advance.

Find the area of a triangular flower garden with sides 11 ft, 19 ft, and 18 ft, to the nearest ten square feet [using Heron's Formula].
• Jan 11th 2009, 05:40 PM
Aryth
First, you find the semiperimeter, which is:

$\displaystyle s = \frac{a + b + c}{2}$

Where a, b, and c are the sides of the triangle in any order.

Then you plug what you get for s into Heron's Formula, which states that the Area (A) of a triangle is:

$\displaystyle A = \sqrt{s(s - a)(s - b)(s - c)}$

All you have to do is plug in the numbers. Good luck.
• Jan 11th 2009, 05:49 PM
TheMasterMind
Quote:

Originally Posted by Intrusion
I thought I knew how to do this, but I keep getting the incorrect answer. Can someone help me out? Thanks in advance.

Find the area of a triangular flower garden with sides 11 ft, 19 ft, and 18 ft, to the nearest ten square feet [using Heron's Formula].

$\displaystyle A=\sqrt{24(24-11)(24-19)(24-18)}$

$\displaystyle A=\sqrt{24(13)(5)(6)}$

$\displaystyle A=\sqrt{9360}$

$\displaystyle A=97ft^2$

(for verification)
• Jan 11th 2009, 06:23 PM
Intrusion
Thanks, that's what I did get also but I guess my book's answer key is wrong.
• Jan 11th 2009, 10:11 PM
Aryth
Not necessarily, what did your book have?