Yes you can!  Follow the steps below:

  1. Position your cursor where you wish to add the slides into your new presentation, then click the Insert tab.
  2. On the ribbon, click the drop-down arrow on New Slide button and choose Reuse Slides.
  3. A navigation pane opens to the right. Click the Browse button and choose Browse file... to locate the presentation containing the slides you want to insert.
  4. Highlight the presentation from the list of files and click Open.
  5. The Reuse Slides pane now displays the slides from the presentation as thumbnails.
  6. To insert a slide, click the thumbnail of the slide.
  7. To keep the slide's original background, check the box for Keep Source Formatting.
  8. When you have inserted all the slides needed, click the "X" at the top, right-hand corner of the Reuse Slides pane to close it.