sum_hash_keys.rb

x = {:group_name=>"Grupo I",
      :subjects=>[
          {:subject=>"Previdenciário", :total_answered=>2, :total_correct=>2, :points=>10,
           :average=>100.0, :average_course=>100.0,
           :leading_knowledges=>[{:name=>"Conhecimento prepoderante 1", :average=>0.0},
                                 {:name=>"Conhecimento prepoderante 2", :average=>0.0},
                                 {:name=>"Conhecimento prepoderante 3", :average=>0.0}]},
          {:subject=>"Previdenciário", :total_answered=>2, :total_correct=>2, :points=>10,
           :average=>100.0, :average_course=>100.0,
           :leading_knowledges=>[{:name=>"Conhecimento prepoderante 1", :average=>0.0},
                                 {:name=>"Conhecimento prepoderante 2", :average=>0.0},
                                 {:name=>"Conhecimento prepoderante 3", :average=>0.0}]}],
                                 :total_points=>10}


 x[:subjects].map{|s| {total_answered: s[:total_answered], total_correct: s[:total_correct], points: s[:total_correct]} }
            .reduce({}){|memo, s| memo.merge(s){|key, oldval, newval|  oldval+newval} }