Math advice on the net

[SCEtoAUX]

I was looking up how many mums plants to fit inside a circle with a 3 feet radius. Doing some cypherin' I came up with an area of around 24 square feet. Most places recommend 11 plants.

This is where it gets stupid. One website had this notation:

Circle - 3.14 x radius squared - (Radius is distance from center of circle to perimeter / or half the distance of the diameter) (Radius squared is radius x 2)

(emphasis added by me)

Radius squared is not radius x 2, it is radius x radius.
I wonder how many people are going to calculate the area of a circle incorrectly using that info.

Pi r squared? No! Pi are round.

[SteveB]

Good point - there's a lot of duff information out there, and an example like this shows there's no substitute for good old fashioned learnin'!

As for pies - I like 'em whatever shape they are :o)

[hornswoggler]

... (Radius squared is radius x 2)

Why are you upset about this? It is not wrong. You just need to make up new units for measuring each time making sure the radius is always measured as "2".
Best
Hornswoggler

[airdave]

Originally Posted by SCEtoAUX

Radius squared is not radius x 2, it is radius x radius.
I wonder how many people are going to calculate the area of a circle incorrectly using that info.

very few, since very few understand what "squared" means in the first place!
And even less know what Pi is these days.
Most will rely on Sketchup to work it out.


But, to your point, I have always been perplexed by why people read this: Pi x R(2) as Pi-R-squared.

I've always understood the solution is Pi times the Diameter(Radius x2)
and yet the common description is always "Radius squared"

Radius = 3"
Rx2 = 6"
Rsquared = 9"

So...would the original calculation not been better defined as Pi times Diameter? Isnt that simpler, and shorter..and easier to remember?

Pizza (Pie) comes round, square, rectangle and pocketed.

[SCEtoAUX]

Pi X Diameter (or Pi X 2r) is the circumference of a circle, not area. I always use Pi X D to figure the circumference instead of Pi x 2r.


Area needs some sort of squre units whether it is square inches, square centimeters, square miles, square kilometers, etc.

[airdave]

oh I just assumed that was a typo on your part (area vs circum.)
and I was just quoting the circumference calculation formula.
I see your original point now..that a website offered the circum. calculation to find area.

still doesnt explain the use of the word "squared" ...lol

area is length times width....lol...that would have been a better (but just as incorrect) answer!


The actual formula is probably something a lot more complicated than pi(R2)
...the formula for calculating circum. of an oval is pretty boggling. I had to use that a few times.

[Lex]

Oval circumference does not even have an analytical expression but there are approximations. I can feel your pain there

[Philip]

My head is starting to hurt...

[kahoody]

Originally Posted by SCEtoAUX

I was looking up how many mums plants to fit inside a circle with a 3 feet radius. Doing some cypherin' I came up with an area of around 24 square feet. Most places recommend 11 plants.

This is where it gets stupid. One website had this notation:

(emphasis added by me)

Radius squared is not radius x 2, it is radius x radius.
I wonder how many people are going to calculate the area of a circle incorrectly using that info.

Pi r squared? No! Pi are round.

Agreed, Doug. Pi r round, but I've found PIZZA to be squared AND round at some establishments.

[whulsey]

I prefer cobblers over pi anyway and they're usually rectangular. Hot blackberry cobbler with a couple of semi-hemispherical scoops of ice cream...Yum!