Thinking Mathematically

1
Thinking Mathematically

• Estimation and Graphs

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Estimation

• The process of getting an approximate answer to a
  question. Different situations require varying
  degrees of accuracy.
• Examples Giving a tip, buying enough beer for a
  party, or what you need on the final to get an A
  in a course.

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Study Tip - Place Value
5 , 2 4 3 , 8 9 7
Ones place
Tens place
Hundreds place
Thousands place
Ten Thousands place
Hundred Thousands place
Millions place
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Graphs and Estimation

• Circle Graphs or Pie Charts going from
  percent to numbers
• Bar Graphs
• Line Graphs

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Rounding Numbers
To round to a particular place

• Look at the digit to the right of the digit where
  rounding is to occur.

2. a. If the digit to the right is 5 or greater,
add 1 to the digit to be rounded. Replace all
digits to the right with zeros. b. If the digit
to the right is less than 5, do not change the
digit to be rounded. Replace all digits to the
right with zeros.
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Rounding Examples
Round 37 to the nearest ten.
If the digit in the place to the right is 5 or
greater, add 1 and replace all digits to the
right with zeros.
40
What if it said round to the nearest 100?
7
Estimation Examples

• You select 4 items at a store costing 2.56,
  4.44, 3.95, 7.22. You have only a twenty
  dollar bill. Do you have enough?
• A woman makes 48,343 a year. Estimate her
  monthly salary. Estimate her weekly salary.

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Other Estimation Techniques

• Pass out handouts and use estimation
  notes for previous text
• Compatible Numbers 4x25?100
• Compensation 48-29 ? 49-30 ? 19
• Front end 278 642 ? 200 600 800
• 53x49 ? 50x40 2000
• Rounding up, down, on 5
• Range 278 642 ? 200 600 800
• 278 642 ? 300 700 1000
• Range estimate is 800-1000