Need math wiz for simple(?) problem

D

DavidK

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Jul 27, 2006
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#1
I have a triangular pond that I need to measure in acres. It measures 285ft, 603ft & 639ft

I added all three sides together, 285+621+621=1527 linear feet
Dividing 1527 into four to create a square of the same linear length= 382per side
The sq footage of a 382 ft square is 145,924
Divide that by 43560= 3.3 acres

Probably not an orthodox method, but it correct?
 
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#2
If you use the two long sides, 603 x 639 for a square measure, then take half=192000/43560=4.4 acres. I realize you don't have right triangle, and I doubt that you have true straight lines along the shore, if you're calculating for something like chemicals, you'll be better off with the a 4.4 than a 3.3, hope this helps.
Wow, when you're wrong you're wrong! Should have been 285 x 621 x .5/ 43560= 2.03
A X B X .5/43560
I originally did b x c in error, sorry about that.
 
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#3
Math is by FAR not my strong suit, but based on those lengths of the three sides of your triangular pond to calculate its area in sq-ft, I get roughly (rounding up) 85,441 sq-ft. (See Heron's Formula...finding an online calc or two will give you the space to input your figures and spit out the numbers just in case I've been asleep at the wheel too long today).

Your math on the total sq-ft in an acre is correct at 43,560/acre, which yields a total acreage of your pond of 1.961 acres.

I shoot a lot better than I "mathimacate" so don't quote me on that. ;)
 
#5
3 replies, 3 different answers! Thanks. I guess that I need an educmication on mathemication.

Since none of you came up with the same average that I did, can anyone tell me why my concept of converting the liner footage of the lake into a square with the same linear footage is not accurate?
 
#6
Base times Height divided by Two then multiplied by the Square Root of the Hypoteneuse which is then added Four times the Quadratic Differential. Or something like that.

Ask Lindy. He knows how to do this. He knows everything. (not saying any of the others is wrong,,,, just helping out with the obstinate perspective) :D
 
#7
ORD said:
Math is by FAR not my strong suit, but based on those lengths of the three sides of your triangular pond to calculate its area in sq-ft, I get roughly (rounding up) 85,441 sq-ft. (See Heron's Formula...finding an online calc or two will give you the space to input your figures and spit out the numbers just in case I've been asleep at the wheel too long today).

Your math on the total sq-ft in an acre is correct at 43,560/acre, which yields a total acreage of your pond of 1.961 acres.

I shoot a lot better than I "mathimacate" so don't quote me on that. ;)
Click to expand...

ok, I found a calculator that uses Heron's formula (thanks ORD) and it gave me 85441 sq feet which is 1.97 acres. Why does converting to a square with the same linear footage not work?
 
#8
Looks like you found Heron's Formula which is correct.

Same linear perimeter shapes do not have the same area. Consider:

5x5 square = 25 area
1x9 rectagle = 9 area
20 circumference circle = 31.83 area
 
#9
I learned something tonight (Heron's formula). I did it by solving for the height of the triangle then using the good ole basic area of a triangle formula. Looks like I was close enough, for gubmint work.
 
#13
Here's what I use to measure acreage.
ACME Planimeter

For example, my pond.

J1vhKPH.jpg
 
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