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## Rounding Numbers

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**Compensation is the rule!**• Solve these problems mentally 4.2 + 3.7 + 5.8 + 4.3 $43.28 - $12.18**Rounding Whole Numbers**Rounding is a useful tool for determining the reasonableness of an answer. There are three basic way to round numbers: • A number may be rounded down • A number may be rounded up • A number may be rounded to the nearest place Use rounding to check to see if your computation makes sense and is in the “ball park” of where your answer should be.**18 X 6 =**If I round 18 to 20 and multiply by this benchmark number, I will get a range of where my answer should be around. 18 is close to 20. If I had 6 twenty dollar bills, I would have $120.00. The answer to 18 x 6 should be close to 120. If my answer varies greatly from 120, I’ll know to check my computation again.**To the Internet**Take out your math notes. Listen carefully to the movie. Write down information you feel is important.**Rounding Rules**Find the place value you are rounding to. • Round 2,384 to the nearest hundred. 2384- the digit 3 is in the hundreds place 2. Look to the digit that is in the place value to the right. 2384**Rounding Rules**2. Look to the digit that is in the place value to the right. 2384 3. The value of the digit on the right will determine if your underlined number will change or stay the same.**Rounding Rules**2384 If the number to the right is 5 or more, you will add one to the underlined digit. 2400**Rounding Rules**The value of the digit on the right will determine if your underlined number will change or stay the same. 2334 If the number to the right is less than 5, you will keep the underlined digit the same and all digits following become zeroes. 2300**Rounding Rules**12,376 round to the nearest thousand. 12376 12376 check the digit to the right 12,000 every thing after becomes zeroes**Rounding Rules**40,126 round to the nearest ten-thousand. 40,126 40,126 check the digit to the right 40,000 every thing after becomes zeroes**Rounding Rules**0.45276 round to the nearest tenth. 0.45276 0.45276 check the digit to the right 0.50000 everything after becomes zeroes 0.5 for decimals – the zeroes can be dropped**Try Your Rounding Skills**The bank calculates the interest earned as $17.218. Round down to the nearest cent. • Find the place you are rounding to. • Look to the digit on the right. • Drop all of the digits to the right of the rounded place. The bank pays $17.22 in interest.**Try Your Rounding Skills**The winning time was 11.437 seconds. Round up 11.437 seconds to the next hundredth of a second. • Find the place you are rounding to. • Look to the digit on the right. • Drop all of the digits to the right of the rounded place. 11.437 seconds is rounded up to 11.44 seconds.**Try Your Rounding Skills**The winning time was 11.437 seconds. Round up 11.437 seconds to the next hundredth of a second. • Find the place you are rounding to. • Look to the digit on the right. • Drop all of the digits to the right of the rounded place. 11.437 seconds is rounded up to 11.44 seconds.**Try Your Rounding Skills**Mr. Wilson is labeling the grocery shelves with unit prices so customers can compare the cost of items. To find a unit price, he divides the quantity by the price. Often, the quotient has more decimal places than are needed so he rounds to the nearest cent (hundredth). $1.23422 is rounded down to ________ $3.89822 is rounded up to __________ $1.865 is rounded up to ___________**More Practice**Please, open your textbook to page 35 and complete problems 9 – 24 with a partner. When you are finished, check your answers with a teacher. When your paper is corrected, you will work on your homework sheet.