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Algebra I Recipe: The Real Number Line
A. Definitions
  1. number line – a line with numbers that are in a sequential order and differ by the same amount. Zero is called the origin, numbers to the left of zero are negative and numbers to the right of zero are positive.
  2. integers – positive and negative whole numbers such as {… -3, -2, -1, 0, 1, 2, 3…}.
  3. opposites – numbers that are the same distance from zero, but on opposite sides of zero,
    such as –5 & 5 OR 7 & -7 OR ¾ & -¾.
    • When opposites are added, the result is always zero.
    • –a is read as the opposite of a.
  4. absolute value – the distance a number is from zero and distance is always positive.
    |-4| = 4, |3| = 3, -|-5| = -5
  5. velocity - tells how fast an object is moving and in what direction.
  6. speed - tells only how fast an object is moving. It is the absolute value of velocity provided the object continues to move in a constant direction.
ExamplesExamples:
A launch pad elevator for a space shuttle drops at a rate of about 12 feet per second. What is its velocity?
A launch pad elevator for a space shuttle drops at a rate of about 12 feet per second. What is its speed?
B. Comparing and Graphing Numbers on the Number Line
  1. To compare two numbers on the number line, graph them and the one on the left is the smallest, the one on the right is the largest.
  2. Numbers go smaller to larger from left to right on the number line.
  3. To graph or plot a number, a darkened circle is put over that number on the number line.
ExamplesExamples:
Write the following numbers in increasing order: 4.8, -2.6, 0, -3, ½, -½
Write the following numbers in increasing order: 7, -½, 2.4, -¾, -5.8, 1/3
Write the following numbers in increasing order: 4.66, 0.7, 4.6, -1.8, 3, -0.66



G Redden

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