[1, 2, 3].inject { |sum, number| sum + number} # 6 # 1 + 2 = 3 # 3 + 3 = 6 [1, 2, 3].inject(2) { |sum, number| sum + number} # 8 # 2 + 1 = 3 # 3 + 2 = 5 # 5 + 3 = 8