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2.NBT.2 Count within 1000; skip-count by 5's, 10's, and 100s.-Framework
http://illuminations.nctm.org/ActivityDetail.aspx?ID=218
http://www.sheppardsoftware.com/mathgames/earlymath/BalloonPopSkip.htm
https://grade2commoncoremath.wikispaces.hcpss.org/2.NBT.2