WordPress: displaying 25 posts from one category and 55 from another

I’m trying to make a loop that will get the latest 25 posts from one category and the latest 55 from another, they need to be in the same loop and the posts are in a isotope filtering system and when it is on ‘all’ it needs to display all the categories in date order not category type>post date, is there a trick for doing this?

Thanks, Harry.

EDIT:
Here is what I currently have for my get_posts loop;

            <?php
            global $post;
            $myposts = get_posts('cat=10,11,49&numberposts=50');
            foreach($myposts as $post) :
            setup_postdata($post);
            $cat_name = '';
            $category = get_the_category();
            $cat_name = $category[0]->slug;
            ?>


            <?php endforeach; ?>

I have tried a few logical things such as;

            $myposts = get_posts('cat=10,49&numberposts=50', 'cat=11&numberposts=50');

But this just returned posts from category 10 and 49.

I thought maybe something like this could work but need the right syntax for it;

      $myposts11 = get_posts('cat=11&numberposts=50');
      $myposts1049 = get_posts('cat=10,49&numberposts=50');
      $myposts = $myposts1049 + $myposts11;