Learning Ruby with Ruby Koans

I've gotten through more than half of the Ruby Koans in the past few weeks. Around the 174th test, the developer is asked to implement a method that solves a trivial problem. I would have liked to make the solution more simple, but this is what I could come up with, based on my current Ruby skill level.

# Greed is a dice game where you roll up to five dice to accumulate
# points.  The following "score" function will be used calculate the
# score of a single roll of the dice.
#
# A greed roll is scored as follows:
#
# * A set of three ones is 1000 points
#
# * A set of three numbers (other than ones) is worth 100 times the
#   number. (e.g. three fives is 500 points).
#
# * A one (that is not part of a set of three) is worth 100 points.
#
# * A five (that is not part of a set of three) is worth 50 points.
#
# * Everything else is worth 0 points.
#
#
# Examples:
#
# score([1,1,1,5,1]) => 1150 points
# score([2,3,4,6,2]) => 0 points
# score([3,4,5,3,3]) => 350 points
# score([1,5,1,2,4]) => 250 points
#
# More scoring examples are given in the tests below:
#
# Your goal is to write the score method.

def get_score_for_matching_roll(potential_roll, dice)
single_scores = {1=>100, 5=>50}
  triple_score_multipliers = {1=>1000}
  single_scores.default = 0
  triple_score_multipliers.default = 100
  triples_singles = dice.find_all { |roll| roll == potential_roll }.size.divmod(3)
  triples_singles[0]*triple_score_multipliers[potential_roll]*potential_roll +
          triples_singles[1]*single_scores[potential_roll]
end

def score(dice)
  # You need to write this method
  score = dice.uniq.inject(0) { |score, potential_roll|
    score + get_score_for_matching_roll(potential_roll, dice)
  }
end