At 10" round with 1.5 × 2 slices will give you 27. 1 x2slices will give you 38 slices.
There are a couple of great apps that I use for this kind of information. They have an app to tell you what cake configuration you will need for a certain amount of servings and then that have an app to show you how to cut the cake to get the servings. I use it all the time.
http://apps.bakingit.com/
Hope this helps.
