Left align and right align within div in Bootstrap

What are some of the common ways to left align some text and right align some other text within a div container in bootstrap?

e.g.

Total cost                   $42

Above total cost should be left aligned text and $42 is right aligned text

2021 Update...

Bootstrap 5 (beta)

For aligning within a flexbox div or row...

• ml-auto is now ms-auto
• mr-auto is now me-auto

For text align or floats..

• text-left is now text-start
• text-right is now text-end
• float-left is now float-start
• float-right is now float-end

Bootstrap 4+

• pull-right is now float-right
• text-right is the same as 3.x, and works for inline elements
• both float-* and text-* are responsive for different alignment at different widths (ie: float-sm-right)

The flexbox utils (eg:justify-content-between) can also be used for alignment:

<div class="d-flex justify-content-between">
      <div>
         left
      </div>
      <div>
         right
      </div>
 </div>

or, auto-margins (eg:ml-auto) in any flexbox container (row,navbar,card,d-flex,etc...)

<div class="d-flex">
      <div>
         left
      </div>
      <div class="ml-auto">
         right
      </div>
 </div>

Bootstrap 4 Align Demo
Bootstrap 4 Right Align Examples(float, flexbox, text-right, etc...)

Bootstrap 3

Use the pull-right class..

<div class="container">
  <div class="row">
    <div class="col-md-6">Total cost</div>
    <div class="col-md-6"><span class="pull-right">$42</span></div>
  </div>
</div>

Bootstrap 3 Demo

You can also use the text-right class like this:

  <div class="row">
    <div class="col-md-6">Total cost</div>
    <div class="col-md-6 text-right">$42</div>
  </div>

Bootstrap 3 Demo 2

Instead of using pull-right class, it is better to use text-right class in the column, because pull-right creates problems sometimes while resizing the page.

In Bootstrap 4 the correct answer is to use the text-xs-right class.

This works because xs denotes the smallest viewport size in BS. If you wanted to, you could apply the alignment only when the viewport is medium or larger by using text-md-right.

In the latest alpha, text-xs-right has been simplified to text-right.

<div class="row">
    <div class="col-md-6">Total cost</div>
    <div class="col-md-6 text-right">$42</div>
</div>

Bootstrap v4 introduces flexbox support

<div class="d-flex justify-content-end">
  <div class="mr-auto p-2">Flex item</div>
  <div class="p-2">Flex item</div>
  <div class="p-2">Flex item</div>
</div>

Learn more at https://v4-alpha.getbootstrap.com/utilities/flexbox/