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Probability rules

Tom’s giant cooler contains 3030 waters and 7070 Cokes. Tom blindly reaches into his cooler and randomly selects a beverage. If the beverage he selects is a water, there is a 90%90\% chance he will drink it. If it’s a Coke, there is only a 40%40\% chance he will drink it.
What is the probability that Tom selects a water and drinks it?
  • Your answer should be
  • an integer, like 66
  • a simplified proper fraction, like 3/53/5
  • a simplified improper fraction, like 7/47/4
  • a mixed number, like 1 3/41\ 3/4
  • an exact decimal, like 0.750.75
  • a multiple of pi, like 12 pi12\ \text{pi} or 2/3 pi2/3\ \text{pi}