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2.NBT.8 Mentally add 10 or 100 to a given number 100-900, and mentally subtract 10 or 100 from a given number 100-900.FrameworkOnline Activities
http://www.ictgames.com/100huntminus10.html
http://www.adaptedmind.com/p.php?tagId=220
http://www.ictgames.com/octopus.html