If the circumference of a circle is doubled, the diameter of the circle

(1) remains the same

(2) increases by 2

(3) is multiplied by 4

(4) is doubled

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- Jan 17th 2007, 04:53 PMsymmetryCircle's Diameter
If the circumference of a circle is doubled, the diameter of the circle

(1) remains the same

(2) increases by 2

(3) is multiplied by 4

(4) is doubled - Jan 17th 2007, 05:20 PMThePerfectHacker
- Jan 17th 2007, 06:20 PMsymmetryok
If the circumference of a circle is 12, the the diameter = pi(12)(d), right?

What whatever the circumference equals, the diameter increases by the same amount, right? - Jan 17th 2007, 07:05 PMThePerfectHacker
- Jan 18th 2007, 12:52 AMearboth
Hello,

you know already that the circumference of a circle is calculated by:

$\displaystyle c=2 \cdot \pi \cdot r= \pi \cdot d$, with diameter = 2 * radius.

Plug in the value you know:

$\displaystyle 12= \pi \cdot d \Longleftrightarrow d=\frac{12}{\pi}$.

In general:

$\displaystyle c=\pi \cdot d \Longrightarrow d=\frac{12}{\pi} \Longrightarrow \pi=\frac{c}{d}$

EB

PS: I've attached a diagram which helps to memorize the right formula: Cover the variable you want to calculate with your fingertip. The remaining term shows how to calculate the covered value. - Jan 18th 2007, 12:57 PMsymmetryok
Thank you for the notes and reply.

Earboth,

Thank you for the picture. I think tutors should use pictures here to help students.