1 3 & 1-4 rounding
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1 3 & 1-4 rounding






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1 3 & 1-4 rounding 1 3 & 1-4 rounding Document Transcript

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