Please help. I know I asked this before. Thanks to all of you who have responded to this. I tried pi r 2 h/231. (Because there are 231 cu. inch in gallon of water.) It's not coming out right. Ok, here's the volume of water I need to figure out. I have a tank that measures 72 inches in diameter by 72 inches high. Thanks again!
2007-02-24 17:56:47 · 7 answers · asked by xoxo 2 in Science & Mathematics ➔ Mathematics
it does work -- here's how.
First calculate the volume in cubic inches. the conversion from cubic inches to gallons is 231 in^3/gallon. The units you've got is volume in cubic inches. So it has to be the equation you've got.
72 inches in diameter is 36 inch radius.
The volume is π(36)^2*72=293148.3 inches cubed. divide by 231 and you get 1269.04 gallons.
2007-02-24 18:05:00 · answer #1 · answered by Rob M 4 · 1⤊ 0⤋
Hello,
First lets clarify something. The formula for the area of a cylinder is:
âr x r x h (where the x's represent multiplication, and r x r is "r squared". The first symbol is Pi (approx. 3.14)
You state your tank is 72 inches in diameter - remember diameter is not the same as r, the radius. d = 2r, so your radius is 36 inches.
Using 36 inches for r, you get:
(3.14) (36in x 36in) x (72in) = 292,999.68 inches cubed (or cubic inches.
divide this number by your 231 cubic inches to find gallons, you should get 1268.4 gallons.
This is the correct number of gallons for the tank dimensions you give. This sounds like a dang big tank - 36 inches is 3 feet in radius, meaning the entire linear length of the tank is 6 feet, while the 72 inches high is 6 feet high - are you sure this is right for the tank dimensions? Is this something you own or a math problem?
Please email or IM me if you have questions. Peace. CCW.
2007-02-25 03:07:41 · answer #2 · answered by Cian 5 · 0⤊ 0⤋
Doesn't anyone know the meaning of significant digits any more? The least accurate input only has two digits, so the answer can only be accurate to two digits, in other words, 1300 gallons. If the measurement was given as 72.0 inches, the answer would be reliably 1270 gallons +/- 5 gallons. To get 1269 gallons, the container must be measured to the nearest 1/100 of an inch!
Just because your calculator gives you ten digits does not make it true (especially if you only use 3 digits for pi, smarties).
Sorry, smarties, it's two *digits*, not two decimal digits. Put another way, two digits gives you and accuracy of up to one part in 100 (from 0 to 99), which a *percentage* which applies to any order of magnitude. Besides that, 3.14 is only an approximation to the value of pi, which goes on indefinitely from 3.14159265... For this reason (if you do it right) both pi and 231 can be considered *exact* numbers - but you did it wrong. Recompute your answer using a more accurate value for pi and you'll see what I mean.
2007-02-25 02:17:50 · answer #3 · answered by hznfrst 6 · 0⤊ 1⤋
The formula is Ï* r^2 *h so you will have:
v= Ï* 36^2 *72
Ï= 3.14
v= 3.14 * 1296 * 72 = 292,999.68
divide that by 231:
292,999.68 / 231= 1268.3969 Gallons
hznfrst, you are both right and wrong. The correct answer is 1268.40 gallons because the Ï is 3.14 which means the significant figure is 0.01 so I have to show up to 2 decimal digits.
2007-02-25 02:09:39 · answer #4 · answered by smarties 6 · 0⤊ 1⤋
I get Ï(36^2)(72)/231.
Is that what you got?
2007-02-25 02:02:26 · answer #5 · answered by Helmut 7 · 0⤊ 0⤋
FWIW, I get
Ï*(36²)*72/231 = 1269.04 gallons.
Doug
2007-02-25 02:06:20 · answer #6 · answered by doug_donaghue 7 · 0⤊ 0⤋
First, convert inches to centimeters.
Then figure it out for liters, and convert to gallons.
2007-02-25 02:05:23 · answer #7 · answered by netthiefx 5 · 0⤊ 1⤋