Cinderella Rule of Rounding

Rounding is Magical!

Have you ever wondered how rounding can be made magical? One strategy I like to use with my students (and is used by many) is the Cinderella Rule of Rounding. The Cinderella Rule of Rounding gives characters to numbers and tells a story in the process. Here’s an example:

Say you are rounding to the nearest hundred in 7,865.

*The number you are rounding to will become Cinderella. Therefore the eight represents Cinderella. Underline the 8.

7, 8  6 5 rounds to 7,900

*Look at the digit to the immediate right of Cinderella. That digit represents the fairy godmother. If the digit is 5 or greater, the fairy godmother has power and can change Cinderella into a new gown (POOF!) for the ball. In this case the 6 rounds the 8 to a 9. Therefore Cinderella will round up.  7,900

*If, however, the digit is 4 or less, the fairy godmother does not have power and Cinderella cannot change her dress for the ball. She will remain the same. In this case, 3 is less than 5 so the 8 stays the same.

7, 8  3 5 rounds to 7,800

*The fairy godmother then disappears leaving only zeros after Cinderella.

*If there are digits to the left of Cinderella, they are her loyal friends (the birds, mice, etc…) and they stay the same.

Try this with your students and hopefully this strategy will click with some and they will find success.  

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