What is the approximate circumference of circle C if PQ = 20 mm? (Use 3.14 for pi.)

Question

n00bstyle · Answer

Hello cmwilso, can you tell me what PQ is?
Is that the diameter of circle C, or is it the radius?

anonymous · Answer

PQ is the diameter of the circle.

n00bstyle · Answer

Alright then

anonymous · Answer

I think that PQ is 9 cm long

n00bstyle · Answer

Let me put it like this, you should just never forget the formules I am about to write down ;)
If you want to know the circumference, you should use the formula: 2*Pi*radius
If you want to know the area of that circle, you should use: Pi*radius^2 (which is the same as 1/4*Pi*diameter^2)

There are a few numbers of deriving these formulas, but they are quite elaborate.

anonymous · Answer

thank you. that was very helpful. :)

n00bstyle · Answer

you will have to use them quite a lot in time, when you continue your study ;)
Try to remember them by heart!
Good luck