Question

What is the radius?

Answer 1

Use the arc length formula for a circle.

Answer 2

I don't have an angle, though.

Answer 3

They give you that the measure of the arc is 120

Answer 4

I divide that by 2?

Answer 5

Wait what does the 7 represent?

Answer 6

The 7 is the length of the arc, and 120 is the measure of the central angle of the circle, with respect to the arc.

Answer 7

Oh. Thank you for the clarification
...

Answer 8

Something's wrong. I got .29

Answer 9

Did you convert the angle to radians?

Answer 10

i was going for degrees.

Answer 11

Convert to radians and then apply the formula.

Answer 12

Sorry but how do you convert to radians? The formula I see is l=(x)r

Answer 13

x being the degree of the angle.

Answer 14

Hmmm. I've never used it with degrees. To convert to radians, multiply by pi/360

Answer 15

So 120*pi/360 then divide by 7?

Answer 16

sorry. Pi/180, not pi/360

Answer 17

If they want it in degrees, then just use degrees.

The equation we have is 7 = (120)*r

Answer 18

17.14 then is the radius?

Answer 19

I divide 120 by 7

Answer 20

I'm so sorry if I'm frustrating you. It's been years since I've worked on this type of math.

Answer 21

You want to solve for r, so divide 7 by 120.

Answer 22

okay I got .058

Answer 23

I suppose thats the answer they want. If you were to do it in radians, you would get 21/pi which is about 6.68

Answer 24

This doesn't make sense...

Answer 25

I'm sorry if i'm being confusing.

Answer 26

Let's give it one more try?

Answer 27

OK. The equation is I = xr, where I is the arc length, x is the angle, and r is the radius.

Answer 28

And you're sure that's the formula to use to find the radius?

Answer 29

Yes. Did I describe the formula you gave correctly?

Answer 30

The arc length formula?

Answer 31

Then yes.

Answer 32

OK. We are given I and we are given x.

Answer 33

http://www.mathsisfun.com/definitions/arc-length.html
study this and let us know if you can't understand thereafter

Answer 34

@nincompoop That's the formula I tried earlier! But I got weird numbers.

Answer 35

\[7 = 120 \times \frac{ \pi }{ 180 } \times r\]
it seems that r can be isolated so easily

Answer 36

I ended up with 7=2.093 (r)

Answer 37

Now my final answer is .029

Answer 38

But it just seem like an odd number and I don't know how to check it.

Answer 39

I plugged the number back in and got .6..........

Answer 40

http://www.wolframalpha.com/input/?i=7+%3D+120+degrees+*+pi%2F180+*+r+

Answer 41

r= 21/2pi

Answer 42

Where did the 21 come from?

Answer 43

It was 3.34....