« Reply #1 on: December 03, 2014, 07:41:40 PM »
The formulas you used are ok for two legs arbs.
You can find these formulas here: http://surebettracker.com/LetsBlog/learning-center/calculating-arbitrages/
You can find the maths explaining the formula here: http://www.surebetmonitor.com/2014/10/02/the-math-behind-arbitrage/
However, most alert services or calculators (or your own excel) will do this for you.
How will you detect these arbs?
The example you provided is probably an error. 11% is too high.
The rounding you used is only valid if the arb percentage is really high. Otherwise you will probably lose money on one bet. If one book is sharp you don't need to round stakes.
Live arbitrage or arbitrage near the start of the match needs much more experience. You should not start there.
100 is really low. I started with 200, but I admit is toooooo low :-)