For an ale with that gravity, you need about 286 billion yeast cells to get a good, strong, clean fermentation without any off-flavors. One white labs vial contains about 100 billion cells if fresh, the longer sionce the production date, the less viability of cells. This is good for anything at 1.048 and under.
A dry packet of yeast contains about 20 billion live cells per gram, if properly rehydrated, meaning correct temperature and amount of water (usually about 1/2cup at100F). If pitched directly onto the wort, you will get about half at 10 billion per gram, and improperly rehydrating can actually be bad, resulting in about 6-8 billiob per gram. This gives you 150 - 300 billion cells per dry yeast package, assuming you don't imporperly rehydrate.
If you make no starter, and don't rehydrate the dry packet, you will have about 250 billion yeast cells by using both, just about right for your beer. If you rehydrate the dry packet, you will only need that. It is the same strain of yeast by the way.