decrease input width (using bootstrap) - html

Question

I am trying to decrease middle name input field but i can't get it work. It only works at xs screen (picture below).
<div class="row">
<form class="form-inline" role="form" name="userForm" novalidate>
<div class="form-group required">
<label for="first" class="control-label">Child's Name</label>
<div class="input-group">
<span class="col-xs-9 col-sm-5">
<input type="text" class="form-control" id='first' name="first" >
<label for ="first">First </label>
</span>
</div>
<div class="input-group">
<span class="col-xs-3 col-sm-2">
<input type="text" class="form-control col-xs-3 col-sm-2" id='mi' name="mi" >
<label for ="mi">MI</label>
</span>
</div>
<div class="input-group">
<span class="col-xs-9 col-sm-5">
<input type="text" class="form-control" id = "last" name="last" >
<label for="last"> Last </label>
</span>
</div>
</div>
</form>
</div>

Answer 1

You're code is wrong please check again.you end the </form> before end other tag. and again read how to use bootstrap form. help this link.

Answer 2

remove span and add col-sm-4 to div
`
<div class="form-group required">
<label for="first" class="control-label">Child's Name</label>
<div class="input-group col-sm-4">
<input type="text" class="form-control" id='first' name="first">
<label for="first">First </label>
</div>
<div class="input-group col-sm-1">
<input type="text" class="form-control " id='mi' name="mi">
<label for="mi">MI</label>
</div>
<div class="input-group col-sm-4">
<input type="text" class="form-control " id="last" name="last">
<label for="last"> Last </label>
</div>
<div class="help-block" ng-messages="userForm.first.$error" style="color:maroon" role="alert">
<p ng-message="required">Child's First Name is required.</p>
</div>
</div>
<div class="form-group">
<button type="submit" class="btn btn-danger">Submit</button>
</div>
</form>`