Equal separation between elements in a div - html

Question

Let's say I have a div, 100px wide, and a variable number (from 1 to 6) of elements, 10px wide, inside that div.
How can I equally space them so that:
if there is 1 element inside, there will be no additional spacing
if there are from 2 to 6 elements, spacing between each would be 80px (for 2), 35px (for 3), 20px (for 4), etc...
The first item will always be placed at the most left position, without padding, and the last item will always be placed at the most right position, also without padding.
I'm not concerned about IE, so this could be CSS3. Anyways, I am concerned about javascript. I know this would be a 1 liner in JS, but I certainly want to avoid it if possible, so please refrain answering if you're going to post a JS solution.
Regards
Edit:
Example: http://codepen.io/anon/pen/wbiFA
HTML
<div class="container">
<div class="item">
</div>
<div class="item">
</div>
<div class="item">
</div>
<div class="item">
</div>
</div>
CSS:
.container {
width: 900px;
border: 1px solid red;
display: flex;
justify-content: space-between;
height: 50px;
}
.item {
border: 1px solid blue;
flex-basis: auto;
width: 171px
}
Ok, did it :)

Answer 1

You don't need CSS3 features like flexible boxes. The following CSS2.1 features are enough:
text-align:justify
display: inline-block
::after pseudo-element
.container {
width: 900px;
border: 1px solid red;
height: 50px;
text-align: justify;
}
.container:after {
content: '';
width: 100%;
display: inline-block;
}
.item {
border: 1px solid blue;
width: 171px;
height: 100%;
display: inline-block;
}
<div class="container">
<div class="item"></div>
<div class="item"></div>
<div class="item"></div>
<div class="item"></div>
</div>

Answer 2

Using Flexbox i managed a close enough result:
http://codepen.io/coljung/pen/bufmh
.container {
border: 1px solid red;
width:1000px;
height:100px;
display: flex;
justify-content: space-around;
}
.item {
border: 1px solid blue;
background:red;
width:100px;
height:100%;
}
Now, it doesnt achieve the exact padding you are looking for. In that case you have to do it manually for every single case.