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Estimation

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Estimation Powered By Docstoc
					             Estimation
GLE 0506.1.2 Apply and adapt a variety of appropriate
strategies to problem solving, including estimation, and
reasonableness of the solution.
���� 0506.1.3 Explore different methods of estimation
including rounding and truncating.
                  Vocabulary
   Digits – a number symbol used to make
    numbers (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
   Numbers – Made up of any combination of digits
   Place Value - The value of a digit based on its
    position in a number
   Truncating - To shorten (a number) by dropping
    one or more digits after the decimal point
   Whole Number – any positive number that does
    not have a fractional or decimal part
Place Value
            Rounding
 In order to estimate an answer,
  we round the numbers in the
  problem to solve
 Look at each digit in the number.
 Determine which place value the
  digit to be rounded is in.
           Rounding

If the digit following that
 number is five or more, round
 up.
If the digit following that
 number is four or less, round
 down.
              Practice
 Round   to the nearest hundred.
 234
 –Since 2 is in the hundreds place, I
  need to look at the 3 to determine
  whether to round up or down. What
  do you think?
 –Since three is less than 5, I should
  round down.
 –200 is the correct answer!
              Practice
 Round   to the nearest hundred.
 769
 –Since 7 is in the hundreds place, I
  need to look at the 6 to determine
  whether to round up or down. What
  do you think?
 – Since 6 is greater than 5, I should
  round up.
 –The correct answer is 800!
              Practice
 Round   to the nearest hundred.
 457
 –Since 4 is in the hundreds place, I
  need to look at the 5 to determine
  whether to round up or down. What
  do you think?
 –Since 5 is equal to 5, I should round
  up.
 –500 is the correct answer!
Think You’ve Got It? Try these!

346            300
589            600
947            900
201            200
197            200
 Another Way to Look at Rounding
 Think of a number line. (You may have
  one in your classroom or on your desk!)
 As you look at the number you are
  rounding, think is it closer to the multiple
  of ten or one hundred below it or above it.
Round   7 to the nearest ten.
Look at the number line.
Is 7 closer to 0 or 10?
7 is closer to 10, so we round
 up to 10.
Round   4 to the nearest ten.
Look at the number line.
Is 4 closer to 0 or 10?
4 is closer to 0, so we round
 down to 0.
           Truncating

We   will use truncating when
 dealing with decimals.
If we want to round a decimal
 number to a whole number, we
 will need to look at the digit(s)
 following the decimal point.
                  Truncating
   Round to the nearest
    whole number
 23.6
                            24
 37.8                      38
 45.2                      45
 61.9                      62
 55.4                      55

				
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posted:2/1/2013
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