all you math guys and girls. help an online sister out.?

Question

if d is the diameter of a circle, then pi(d)^2 represents...
.the area of the circle
.half the area of the circle
.twice the area of the circle
.one-fourth the area of the circle
.four times the area of the circle

Answer 1

if d = 2 * r

then

pi * (2*r) ^ 2
pi * 4 * r ^ 2
4 * (pi * r ^ 2)

What is pi*r^2?

Answer 2

pi*r^2 is a familiar formula for the area of a circle, where r is the radius (or half the diameter) of a circle. In order to use the diameter to find the area of a circle, you can use the formula (pi*d^2)/4. Multiplying the equation by 4 will give you your original equation of pi*d^2. So, the answer is the last one, or pi*d^2 is four times the area of a circle.

Hope this was helpful and not too confusing.

Answer 3

Pi r^2 = the area of a circle.
d = diameter = 2 r = 2 radii
Pi d^2 = Pi (2r)^2
Pi (2r)^2 = 4 (Pi r ^ 2) = 4 x area of the circle

Answer 4

OK...We know Area (A) of a circle is Pi x r^2. We also know that r = d/2. put d/2 in the Area formula, and you get A = Pi x (d/2)^2. Multiply through, and you get A = Pi x [(d^2)/4)]. Multiply the whole thing by 4 to get rid of the fraction, and you get 4A = Pi x d^2. So we answered the question....4 TIMES THE AREA = d^2 !

Good luck.

Answer 5

you would have 4x the area of the circle.

lets say r=2 (r is radius, half the diameter), then the area of the circle would be pi*2^2 or 4pi...and since d is double r, then d would =4, thus pi*d^2 is pi*4^2 or 16pi...thus 4 times that of the true area

Answer 6

four times the area of the circle

because...

the diameter is twice the radius >>>>> (d=2r)
so put 2r in place of the d >>>>> pi(2r)^2
so it's >>>>> pi(2^2)(r^2)
so that is >>>>> 4pi(r^2)
and pi(r^2) is the area
so it is 4 times the area

Answer 7

d = 2r if r is the radius of the circle
Then pi(d)^2 = pi(2r)^2
(2r)^2 = 4r^2, so now you have pi(4r^2), or 4pi(r^2).
Since pi(r^2) is the area of the circle, this is 4 times the area

Answer 8

Well pi(d) is the area*.... Pi(d)^2 is half the surface area of a sphere.

http://www.1728.com/diamform.htm