Oh, and you mentioned you were making a sampler which is how I taught myself to quilt. Quilter's Cache is probably one of the best sites on the web to find blocks by size. Here is the link to all the 12" blocks.
http://www.quilterscache.com/BlocksbySizeC.html
If you really like the 10" versions though and don't want to do the math to enlarge them--by all means feel free to add a one inch border to the pattern you have. It's a sampler so it won't matter. They're all supposed to be different.