Recently I was asked to share some sites that could help with basic fact facts at the K-3 level. I will gladly share them, but must caution that they should not be given without addressing math strategies.
Efficient strategies can be done mentally and quickly. Counting is not efficient by itself. If drill is undertaken when counting is the only strategy that a student has to work with, all you will get is faster counting. Drill of inefficient methods does not produce mastery.
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Basic Operations http://www.sheppardsoftware.com/math.htm
(note Early Math K-2 button at top)
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Math practice (all operations) http://www.playkidsgames.com/games/mathfact/mathFact.htm
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Number line addition http://www.sheppardsoftware.com/mathgames/earlymath/fruit_shoot_NumberLine.htm
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Number Line subtraction http://www.sheppardsoftware.com/mathgames/earlymath/FS_NumberLine_minus.htm
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Guess the number http://www.funbrain.com/guess2/index.html
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Number Twins (adding to make 5 or select harder- harder than it seems great challenge) http://www.sheppardsoftware.com/mathgames/numbertwins/numbertwins_add_5.htm
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World Cup Math all operations http://mrnussbaum.com/football/
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Math Flash cards (all operations) http://www.factmonster.com/math/flashcards.html
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100 square http://resources.woodlands-junior.kent.sch.uk/maths/interactive/numbers.htm
and http://www.oswego.org/ocsd-web/games/dogbone/gamebone.html
or http://www.abcya.com/100_number_grid.htm
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Adding activities http://resources.woodlands-junior.kent.sch.uk/maths/interactive/index.htm
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Addition flashcards and more http://www.learninggamesforkids.com/math_addition_games.html
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Subtraction flash cards and more http://resources.woodlandsjunior.kent.sch.uk/maths/interactive/subtraction.htm
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Fun 4 The Brain http://www.fun4thebrain.com/addition.html
(note menu at top to select operation)
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Math all grades http://ca.ixl.com/promo?gclid=CPP5gomCiLYCFaI7MgodmwYACw&phrase=Search+-
+math&partner=google
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Very visual, basic addition http://www.softschools.com/math/addition/learning_addition_for_kids/ and http://www.sheppardsoftware.com/mathgames/earlymath/CountAnimals1to5.htm
and http://www.sheppardsoftware.com/mathgames/earlymath/bugabalooShoes.htm
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Very visual, basic subtraction
 http://www.sheppardsoftware.com/mathgames/earlymath/subHarvest.htm
http://www.factmonster.com/math/flashcards.html