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**KIRA c:****Guest**

I've been trying to do these for a while and just can't figure them out. I've asked my parents, but they don't know either, soI asked my teacher and they told me to just use the equation, which I have been doing, so that was no help.

Formula is:

L = (n/360)(2(PI)r)

Where:

L = Length, n = degree measure of arc, r = radius of the circle.

In these questions I need to find the arc length.

11. r=10 n=20

A) 15(pi)/ 7

B) 13(pi)/ 5

C) 16(pi)/ 2

D) 11(pi)/ 4

E) 10(pi)/ 9

F) 9(pi)/ 4

So, I set up the equation L = (20/360)(2(PI)10). Then I reduced the first part, L = (1/18)(20(PI)). So the answer would be 20(PI)/18? I'm just so lost on this.

Other Questions That are Similar That I Don't Understand:

12. r=3 n=6

A) pi/9

B) pi/12

C) pi/26

D) pi/10

E) pi/8

F) pi/4

13. r=4 n=7

A) 8(pi)/55

B) 6(pi)/12

C) 7(pi)/45

D) 2(pi)/22

E) 9(pi)/18

F) 7(pi)/37

14. r=2 n=x

A) x(pi)/15

B) x(pi)/30

C) x(pi)/60

D) x(pi)/90

E) x(pi)/120

F) x(pi)/150

Then, how would you find the radius if:

16. n=30 L=1/3xy(pi)

A) 6xy

B) 8xy

C) 2xy

D) 10xy

E) 3xy

F) 14xy

I don't know how to do this one at all.

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,771

Hi;

So, I set up the equation L = (20/360)(2(PI)10). Then I reduced the first part, L = (1/18)(20(PI)). So the answer would be 20(PI)/18? I'm just so lost on this.

Try reducing 20 / 18. Then it will look like answer E.

12) I have D.

13) C

14) D

For 16, do you mean?

*Last edited by bobbym (2013-02-18 19:48:57)*

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**KIRA c:****Guest**

I submitted it and got a 19/20! Thanks everyone!

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,771

Hi;

Congratulations, that is a nice score.

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

**Online**

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