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Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Introduction to Ratios
This video introduces and explains the concept of ratios through a number of examples. Practice problems are available. [14:13]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Solving Percent Problems 3
This video demonstrates how to find the base number when given a percentage and amount. Practice problems are included. [5:26]
Khan Academy
Khan Academy: Arithmetic and Pre Algebra: Finding Unit Rates
This video shows how to find a unit rate in the context of a word problem. Practice problems are available. [2:31]