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Rounding Whole Numbers: Math Strategies
Rules For Rounding
When the ARROWED number is 0 – 4, the circled number STAYS THE SAME. When the ARROWED number is 5 – 9, the circled number goes up by 1. Every number after the circled number changes to zeros.
This strategy for rounding requires that students already know place values. If your students have not learned place values, teach place value first; then come back to rounding. (Note: I have presented place value teaching tips and strategies in the article: PLACE VALUES of WHOLE NUMBERS.)
When I teach students rounding, I never use the phrase GO DOWN. Instead, I use STAYS THE SAME. In actuality, that is what happens. The circled number stays the same; not go down.
Practice the rules for rounding. Make sure that students understand and are able to apply them when rounding.
Circle and Arrow Strategy – Have students circle the place value they are rounding to, i.e. nearest ten, hundred, thousand, etc. Place an arrow above the number immediately following the circled number.
Example: Round 638 to the nearest hundred.Circle the 6 and place an arrow above the 3. (This is why students MUST know place values.)
Let students know that the arrowed number MUST tell the circled number what to do. You can easily turn this into a FUN game for students. The arrowed number can be the student and the circled number a sibling or friend of the student; or the arrowed number can be the BIG BOSS. In either case, students must understand that it’s the arrowed number that is in charge of what happens to the circled number.
Refer to the Rules for Rounding to decide what the arrowed number is going to tell the circled number to do. In this example the arrowed number will tell the circled number to stay the same and every number after the circled number changes to zeros.
So, the correct answer is: 638 rounds to 600.
Have fun using this strategy. It works and the children have fun rounding to any given place value because they get to be the BIG BOSS or the one making the decision about what to do!!