Circumference and Area of Circles
posted by mike on .
can someone help me with these:Find the radius, diameter and circumference of a circle with an area of 64 cm2. Write your answers as decimals rounded to the nearest hundredth.
Find the circumference and area of a circle that has a rectangle inscribed inside it with sides that are 9 by 12 centimeters. Write your answer as decimals rounded to the nearest hundredth. (hint: Draw this circle on your paper and find the length of the diagonal of the rectangle.)
you should know that Area = πr^2
and circumference is 2πr
and clearly the diameter is 2r
ao πr2=64
r = 8/√π
evaluate using your calculator and substitute in the above expressions.
Round off AFTER you have substituted,not before.
For your second question they have given you an excellent hint.
I will give you one more...
the radius of the circle is half the length of the diagonal of the rectangle.

a 9x12 rectangle has diagonals of
d = ã(9^2 + 12^2) = ã225 = 15
since these diagonals are also the diameter off the circle
A = ƒÎ (d/2)^2 = ƒÎ (15/2)^2 = 176.7
C = ƒÎd = ƒÎ(15) = 47.123 
a 9x12 rectangle has diagonals of
d = square root of(9^2 + 12^2) = square root of 225 = 15
since these diagonals are also the diameter off the circle
A = pi (d/2)^2 = pi (15/2)^2 = 176.7
C = pi times d = pi(15) = 47.123 
This question Find the circumference and area of a circle that has a rectangle inscribed inside it with sides that are 9 by 12 centimeters. Write your answer as decimals rounded to the nearest hundredth. (hint: Draw this circle on your paper and find the length of the diagonal of the rectangle.) is copyrighted material of Florida Virtual School. Please remove it and any solutions.

None of these are correct! Try doing your own work instead of copying off of stupid people that don't understand math!!!

waht do we do on circumfrence?