1 3 & 1-4 rounding


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1 3 & 1-4 rounding

  1. 1.
  2. 2. 1-3 Estimating by Rounding Up or Rounding Down<br />1-4 Estimating by Rounding to the Nearest<br />Round any decimal up or down.<br />Round any decimal to the nearest value of a decimal place.<br />On August 29, 2005, Hurricane Katrina <br /> ripped through Louisiana with a Category <br /> 5 storm. The hurricane caused severe<br /> devastation in 80% of the major coastal <br /> cities. The damage was estimated at <br /> $76 billion, and about 1,600 people lost <br /> their lives. <br />What are some other examples <br />of a situation where an estimate might <br />be preferred over an exact value?<br />
  3. 3. Why are estimates needed?<br />1.An exact value may not be worth the trouble it would take to get it.<br /> For example:<br /> About 30,000 people attended the baseball game.<br />2.An estimation is often easier to work with than the exact value.<br /> For example:<br /> Instead of multiplying $169.95, let's use $170.<br />3.It may be safer to use an estimate than to try to use an exact value.<br /> For example:<br /> The home repairs will cost at least $18,000 as a result of the hurricane. So we will budget $20,000 to play it safe.<br />4.An exact value may change from time to time, forcing an estimate.<br /> For example:<br /> I estimate that the coin will land tails 5 times in 10 tosses.<br />5. Predictions of the future or notions about the past usually are estimates, since exact values may be impossible to obtain. <br /> For example:<br /> One estimate of the world population in the year 2025 is 12 billion.<br />
  4. 4. 4 Methods of Rounding<br />**Rounding is the most common way of estimating.**<br />*Rounding is done with a particular decimal place in mind.**<br />Rounding UP - "to the next;" going to the higher point of the interval<br />Rounding DOWN - "to the preceding;" going to the lower point of the interval<br />Truncate - round down, or cut off<br />1325<br />1400<br />1300<br />900<br />1325 Truncated to the tens place: 1320<br />**Some calculators truncate long decimals to the preceding millionth (6 decimal place). <br />For example: <br />π = 3.1415926535 <br /> a calculator might truncate it to show 3.141592<br />Rounding to the NEAREST - given a decimal place, look to the value after it:<br /> if the value is 5 or greater, round up to the next number<br /> if the value is 4 or less, truncate<br />Round 1325 to the nearest ten:<br />1330<br />Round 1325 to the nearest thousand:<br />1000<br />
  5. 5. Round up or down.<br />Example 1:<br />Round 10.4554 up to the next ten.<br />Round 10.4554 down to the previous tenth. <br />
  6. 6. Round to the nearest.<br />4 or less, round down (truncate)<br />5 or greater round up (next)<br />Example 2:<br />465,877,912.556 734 603<br />Round to the nearest million.<br />Round to the nearest tenth.<br />Round to the nearest ten thousandths.<br />Round to the nearest unit.<br />
  7. 7. What method should you use?<br />Example 3:<br />A certain type of CD-RWs are available only in 15 count packages. How many packages would you need to buy if you were to make a copy of your debut performance for each of your 110 classmates?<br />Example 4:<br />A cargo plane can carry 10,500 lbs. What weight limit may be placed on the cargo to be sure that the actual limit is not exceeded? <br />Example 5:<br />Pencils are sold in packages of 10. I need one pencil for each student in a class of 27. <br />How many pencils must be bought?<br />Example 6:<br />The product of 0.1349 and 0.00024 is 0.000032376. What will a calculator with an 8-digit display and that rounds show for the answer?<br />Example 7:<br />My savings account earns monthly interest. My bank rounds down any fractions of a <br />cent on interest paid on a savings account. How much interest would be paid if the calculated amount is $75.625?<br />Example 8:<br />Giant Eagle sells avocados at three for $1. You want just one. So you divide $1.00 <br />by 3 to get the cost. Your calculator shows 0.333333. How must will you probably <br />have to pay for the avocado?<br />Example 9:<br />The U.S. Interval Revenue Service allows taxpayers to round all amounts to the nearest dollar. In figuring income tax, to what value can you round each amount?<br /> a. $89.46 b. $165.50 c. $100.91 d. $5,324.28<br />Example 10:<br />Avatar blue-ray costs $27.49 and John wants to buy 7. How he can use rounding to estimate the cost?<br />Example 11:<br />The total U.S. population as of 3:04pm on Sunday, September 12, 2010, was <br />310,230,947. Round this number to the nearest ten thousand.<br />
  8. 8. Tonight's Homework/Practice:<br />Lesson Master 1-3A<br />Lesson Master 1-4A<br />