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The circumference of a circle is 31.4 feet. What is the area of the circle? Explain how you found your answer.
 one year ago
 one year ago
The circumference of a circle is 31.4 feet. What is the area of the circle? Explain how you found your answer.
 one year ago
 one year ago

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dave0616Best ResponseYou've already chosen the best response.1
First off you will need to know the formula for the area of a circle, which is A=pi*radius*radius. next you will need to know the formula for the circumfrence of a circle, which is 2*pi*r=Circ. You know that circumfrance is equal to 31.4 feet, so set that equal to the equation for circumfrence to find r. \[31.4 ft = 2*3.14*r\] because pi is equal to 3.14. Multiply 3.14 by 2 to get 6.28. 31.4 ft = 6.28*r divide 31.4 by 6.28 and you will get r. 5 ft = r. you will then take that information and put it into the equation to find the area: A=pi*r*r A=pi*5*5 can you figure out Area from there?
 one year ago

nynic819Best ResponseYou've already chosen the best response.0
no..I do not understand. Sorry
 one year ago

dave0616Best ResponseYou've already chosen the best response.1
thats fine, the only i can help you more is if you tell me if you dont understand. Ok so you are looking for area, and the formula for the area of a circle is always: Area= pi*radius*radius. but you are given circumfrance. do you have it up until there?
 one year ago

dave0616Best ResponseYou've already chosen the best response.1
ok, you are given the circumference of the circle, at 31.4 feet. The formula for the circumference of a circle is always C=2*pi*r. and you are given circumference, so set the equation to the value given to give you the formula: 31.4 feet = 2* pi * radius. Are we clear up until here?
 one year ago

dave0616Best ResponseYou've already chosen the best response.1
ok, so we need to solve for radius because that is what we need for the equation of area. both 2 and pi are constants, so we can multiply pi by 2, and divide 31.4 feet by the product of 2 and pi, so the work will look like this: 31.4 feet = 2*pi*radius 31.4 feet = 6.28* radius (6.28 because has an accepted working value at 3.14) now divide 31.4 by 6.28 5= radius. Clear up until this point?
 one year ago

dave0616Best ResponseYou've already chosen the best response.1
ok, so you now know that the formula for area is A=pi*radius*radius. Solve for area now that you solved for radius. Can you figure this out?
 one year ago

nynic819Best ResponseYou've already chosen the best response.0
pi *5*5 = 3.14 x 5 x 5 = 81 ?
 one year ago

dave0616Best ResponseYou've already chosen the best response.1
not quite, you have the equation set up right, i would just punch that back into a calculator, because i am getting a number that is close to that, but not exactly
 one year ago

nynic819Best ResponseYou've already chosen the best response.0
Not using a calculator...lol
 one year ago

nynic819Best ResponseYou've already chosen the best response.0
78.5 my mistake...lol
 one year ago

nynic819Best ResponseYou've already chosen the best response.0
So that is my answer? 78.5?
 one year ago

dave0616Best ResponseYou've already chosen the best response.1
yes, the answer is 78.5
 one year ago

nynic819Best ResponseYou've already chosen the best response.0
and if I needed the diameter I would divide in half?
 one year ago

dave0616Best ResponseYou've already chosen the best response.1
nope, diameter is two times the radius. so you would multiply by 2
 one year ago

dave0616Best ResponseYou've already chosen the best response.1
but the formulas do not use diameter, so if you are given diameter, you must divide diameter by 2 to get the radius. dont use diameter when you have to use radius
 one year ago

nynic819Best ResponseYou've already chosen the best response.0
ok. Thanks. That's helped alot. Have to go to bed now. Big test tomorrow. Wish me luck :) Have a great night :)
 one year ago
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