What is the perimeter....

[eddy2017]

On the diameter line mark the center, small radius, large radius. This should answer your question.

let's see if I have it right.

 

[lev888]

let's see if I have it right.

Mark _exactly_ the small and the large radius to the left of center. Show their lengths.

 

[eddy2017]

Mark _exactly_ the small and the large radius to the left of center. Show their lengths.

R=10
r=5

 

[lev888]

R=10
r=5

The diagram is not clear. By marking a radius I mean: mark the center of the circle (I see it), mark a point on the circle (not clear), connect them - that's the radius. Then show its length value (not shown).

 

[eddy2017]

The diagram is not clear. By marking a radius I mean: mark the center of the circle (I see it), mark a point on the circle (not clear), connect them - that's the radius. Then show its length value (not shown).

okay. thanks

 

[lev888]

okay. thanks

Do you see now what the radius segment end points are? Do you see how the straight segments from the problem and the two radii are related?

 

[eddy2017]

Do you see now what the radius segment end points are? Do you see how the straight segments from the problem and the two radii are related?

thank you for taking the time to do that. i had done the same thing but with the arrows the endpoints are much clearer. the straight segments are part of the radius, right?

 

[eddy2017]

thank you for taking the time to do that. i had done the same thing but with the arrows the endpoints are much clearer. the straight segments are part of the radius, right?

then for the larger circle the radius is 10, right?

 

[lev888]

then for the larger circle the radius is 10, right?

What do you mean by "then"? You know the small and the large radius. You don't know the straight segments' length. Can you calculate it? Do you see how this length and the two radii are related?

 

[eddy2017]

What do you mean by "then"? You know the small and the large radius. You don't know the straight segments' length. Can you calculate it? Do you see how this length and the two radii are related?

yes, I see it, Mr Lev. i do. the two straight lines measure the same. they measure 5 inches each
they are half of the diameter which is 10.

 

[lev888]

yes, I see it, Mr Lev. i do. the two straight lines measure the same. they measure 5 inches each
they are half of the diameter which is 10.

I don't understand. Can you answer my question? How are r, R and the length in question related?

 

[eddy2017]

I don't understand. Can you answer my question? How are r, R and the length in question related?

I don't understand. Can you answer my question? How are r, R and the length in question related?

They are part of the length. It is all i can reason.

 

[lev888]

They are part of the length. It is all i can reason.

I don't understand what you mean. If the length is L, can you write an expression that relates r, R and L?

 

[eddy2017]

I don't understand what you mean. If the length is L, can you write an expression that relates r, R and L?

I am sorry. I do not know.

 

[lev888]

I am sorry. I do not know.

A-------B-------------C

How about lengths of AB, BC, AC?

 

[nasi112]

I am sorry. I do not know.

The main idea lev888 is telling you is that take the big [MATH]R[/MATH] subtract from it the small [MATH]r[/MATH], you will get [MATH]1[/MATH] straight line.

Like this [MATH]R - r = 1[/MATH] straight line

But you have two straight lines, then

[MATH]R - r + R - r = 2R - 2r[/MATH] as I have shown in my formula.

 

[eddy2017]

The main idea lev888 is telling you is that take the big [MATH]R[/MATH] subtract from it the small [MATH]r[/MATH], you will get [MATH]1[/MATH] straight line.

Like this [MATH]R - r = 1[/MATH] straight line

But you have two straight lines, then

[MATH]R - r + R - r = 2R - 2r[/MATH] as I have shown in my formula.

oh, great. that answers another doubt i had. why the that subtraction of the two radii.
thanks to all of you for your help!.
i went away and studied a little bit of prealgebra as all of you suggested. I think I'm better prepared but still a long way to go. i continue to study pre-algebra and also algebra 1.
thanks again to everyone.

 

[Steven G]

Thanks to you both for replying. so radius would be equal to,
√r =√(314/3.140)
√r=√100
r=10
the radius of the larger circumference is 10

now I have to find the radius of the smaller circle. any hint for that?

Pi is not 3.14 and certainly not 3.140 (where did you get 3.140 from?).

 

[eddy2017]

i know that. i know that the value of pi is equal or approximately equal to 3.14159
but I the problem states 'use pi ≈3.14. ( I forgot it to put it in when I typed it)
now that you mention this, and I know you know that, for years, and I am back now to the time when I was a full time student, math teachers have taught that pi is 3.14 or approximate 3.14 for years.
if I added a 0, that was a typo. thanks for bringing that to my attention.

 

[Deleted member 4993]