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Rounding whole numbers and Decimals

Rounding whole numbers and Decimals. The purpose of rounding…. Why do we use rounding? We round numbers to make them shorter or simpler. Can you think of a scenario when we would need to make a number shorter?

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Rounding whole numbers and Decimals

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  1. Rounding whole numbers and Decimals

  2. The purpose of rounding… • Why do we use rounding? • We round numbers to make them shorter or simpler. • Can you think of a scenario when we would need to make a number shorter? • Anytime we need to estimate or get an approximate number, rounding should be used. • For example: You are at the mall and only have $30. Your lunch is $5.95, you buy a game for $19.99, and you want to see a movie that costs $8.50…do you have enough money?

  3. Copy these steps Rules for rounding whole numbers… • Determine which digit (the place value) is your rounding number and underline it. • Look to the right of the underlined number: *if the number to the right is 0,1 , 2, 3,or 4, then you do not change the rounding digit and all other digits to the right become zeros. *if the number to the right is 5, 6, 7, 8, or 9, then you add 1 to the rounding digit and all other digits to the right become zeros. Examples: 6, 5 3 2 this now becomes 6, 5 3 0 1 0, 7 9 4 this now becomes 11, 000

  4. Copy these steps Rules for rounding decimals… • Underline the rounding digit and look to the number on the right. • If the number is 0, 1, 2, 3, or 4, then you do not change the underlined number and delete all of the other numbers to the right. • If the number is 5, 6, 7, 8, or 9, then you add 1 and drop all of the other numbers to the right. *the numbers in front of the underline number always stay the same, unless you add 1 to the number 9. Example: 53.864 becomes 53.86 603.5678 becomes 603.6 45.698 becomes 45.7

  5. Ready, set, go… • Now let’s practice a few problems together Round the following numbers to the indicated place value; 345,678 to nearest thousand 34,456,789 to nearest hundred thousands 34.5678 to the nearest thousandths 0.04567 to the nearest tenths 0.99978 to the nearest thousandths

  6. More Practice • Come up with four numbers , two whole numbers and two decimals. Rounded each number to different place values. Have your partner round same numbers and compare answers.

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