Ruby/Array/inject

collection = [ [1, "one"], [2, "two"], [3, "three"],
               [4, "four"], [5, "five"]
             ]
collection.inject({}) do |hash, value|
  hash[value.first] = value.last
  hash
end
p collection
# => {5=>"five", 1=>"one", 2=>"two", 3=>"three", 4=>"four"}

collection = [1, 2, 3, 4, 5]
collection.inject(0) {|sum, i| sum + i}       # => 15

%w[pea queue are].inject(0) {|total, word| total + word.length }  # => 11