Making circle appear

[Dung Ping]

I am trying to draw two circles in following page:

http://www.pinyinology.com/svg/fangfa.svg

But the curve line of the left circle disappears inside the right one.
My question is: How to make the line to appear to become a full circle?
Following is the code:

<svg width="200" height="200" version="1.1"
xmlns="http://www.w3.org/2000/svg">

<circle cx="100px" cy="100px" r="40px" stroke="red" stroke-width="2px"
fill='white'/>

<circle cx="120px" cy="100px" r="40px" stroke="blue" stroke-width="2px"
fill='white'/>

</svg>

Thanks.
A beginner

[Martin]

In the 2nd circle, change fill='white' to fill='none'.

Post by Dung Ping
<svg width="200" height="200" version="1.1"
xmlns="http://www.w3.org/2000/svg">
<circle cx="100px" cy="100px" r="40px" stroke="red" stroke-width="2px"
fill='white'/>
<circle cx="120px" cy="100px" r="40px" stroke="blue" stroke-width="2px"
fill='white'/>
</svg>

[Dung Ping]

Post by Martin
In the 2nd circle, change fill='white' to fill='none'.

Thanks for prompt teaching.

Post by Martin

Post by Dung Ping
<svg width="200" height="200" version="1.1"
xmlns="http://www.w3.org/2000/svg">
<circle cx="100px" cy="100px" r="40px" stroke="red" stroke-width="2px"
fill='white'/>
<circle cx="120px" cy="100px" r="40px" stroke="blue" stroke-width="2px"
fill='white'/>
</svg>