Common Core Math 5.nf.7b
Number And Operations - Fractions: Apply And Extend Previous Understandings Of Multiplication And Division To Multiply And Divide Fractions.
Interpret division of a whole number by a unit fraction, and compute such quotients. For example, create a story context for 4 / (1/5), and use a visual fraction model to show the quotient. Use the relationship between multiplication and division to explain that 4 / (1/5) = 20 because 20 x (1/5) = 4.