Here's a link to a simple Geometric Distribution Calculator without a histogram or table
Here's a link to a Geometric Distribution Calculator with Histograms
Curious about where the 10% condition comes from? It's usually beyond the scope of a beginner statistics class, but for those of you who are mathematically adventurous, here's the proof from the University of Texas at Austin.
Here's a link to that coin flipping simulator I used in the video.