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2.2.0 :011 > (50..99).each{|x| puts "#{x}+#{x}=#{2*x}" if x%10 == 2*x/100 && 2*x/10%10 == 2*x%10 }
61+61=122
=> 50..99
# ab+ab = bcc
# x%10 == 2*x/100 即:x的个位要等于2x的百位
# 2*x/10%10 == 2*x%10 即:2x的十位和个位数字要相同 cc