1. ## [SOLVED] Radius, Area And Circumference- Help!

If a circle has a radius of 8.6 cm., find it's area and circumference.

2. Originally Posted by Jangalian
If a circle has a radius of 8.6 cm., find it's area and circumference.

A = pi r^2.
C = 2pi r.

Sub r = 8.6 cm.

Since you're self-confessed clueless, my advice is to get a clue - these two formulae should be known to you (hopefully they are now, anyway).

3. Area = pi*r^2
Circumference = pi*d
d is the diameter, which is equal to twice the radius, as such C = 2pi*r is also an acceptable formula for the circumference of a circle.

I assume that you've already got the answers since Mr. Fantastic gave you the formulas, so if you want to make sure you've done it correctly:

A = pi*r^2
A = (3.14)*(8.6)^2
A = (3.14)*(73.96)
A = 232.2344 cm^2

C = 2pi*r
C = 2(3.14)(8.6)
C = 6.28(8.6)
C = 54.008 cm

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