Q: Which drawable folder does a high density phone default to? If I have an extra-high-quality image in the drawable-xhdpi folder and a medium-quality image with the same name in the drawable-mdpi, which of the two would a high density phone use?

Edit 1: Nanne's answer does not answer my question. His quoted passage relates to screen size whereas my question relates to screen
  density. I followed the link provided by Nanne (thanks Nanne) and did
  find this useful passage however:
"... you do not need default drawable resources when you provide
  alternative drawable resources with the screen density qualifier. Even
  without default drawable resources, Android can find the best match
  among the alternative screen densities and scale the bitmaps as
  necessary..."
But!! it just says (vaguely) Android will find the best match. Anyone
  know what that best match would be as per my question?
Edit 2: A bit of background on Nanne's request: I have a project to which I have added medium, high and extra-high density versions of
  images. My apk size is now ever so slightly over 20MB and I would like
  to keep it below 20MB. I would like to remove some images from either
  the mdpi, hdpi or xhdpi folder in a way that images still scale
  and look ok on all density phones, but am not sure which folder to
  remove some of the images from...


A: From this page

When selecting resources based on the screen size qualifiers, the
  system will use resources designed for a screen smaller than the
  current screen if there are no resources that better match (for
  example, a large-size screen will use normal-size screen resources if
  necessary). However, if the only available resources are larger than
  the current screen, the system will not use them and your application
  will crash if no other resources match the device configuration (for
  example, if all layout resources are tagged with the xlarge qualifier,
  but the device is a normal-size screen).

So it should use the medium one.
