Pearson Algebra 1 Common Core, 2011
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Pearson Algebra 1 Common Core, 2011 View details
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Exercise 35 Page 70

Can a repeating decimal be rewritten as a fraction?

Rational number

Practice makes perfect

Before we consider the given number, let's recall the various types of numbers.

  • Rational Number: A number is a rational number if it can be written in the form ab, where a and b are both integers and b≠ 0.
  • Integer: A number is an integer if it is a positive or negative counting number (or zero). All integers are also rational numbers because any number can be written as a division by one, a1.
  • Whole Number: A number is a whole number if it is a non-negative counting number. All whole numbers are also integers and rational numbers.
    • Natural Number: A number is a natural number if it is a positive counting number. All natural numbers are also whole numbers, integers, and rational numbers.
    • Irrational Number: An irrational number is a number that cannot be written in the form of a rational number. These are recognized as being non-repeating, infinite decimals.

    Now, let's try to categorize the given number using these definitions. 0.57 Note that the given expression is an infinite repeating decimal. 0.57=0.575757... All repeating decimals are rational numbers since they can be rewritten as a fraction of form ab, where a and b are integers and b≠ 0. Therefore, we can classify the number as a rational number.

    Extra

    Writing 0.57 as a fraction
    To demonstrate that 0.57 is a rational number, we will rewrite it in the form ab, where a and b are integers and b≠ 0. The expression 0.57 is the same as 0.575757... where 57 repeats infinitely many times. Let x be the number. x=0.575757... By multiplying both sides of the equation by 100, we create a new equivalent equation.

    x=0.575757...
    x* 100=0.575757... * 100
    100x=57.575757...

    Now, we are going to subtract x from both sides. In the next step, we will isolate it.

    100x=57.575757...
    100x-x=57.575757...-x
    99x=57.575757...-x
    x=57.575757...-x/99

    Finally, by substituting 0.57 for x, we can eliminate the repeating decimals on the right-hand side.

    x=57.575757...-x/99
    0.575757...=57.575757...- 0.575757.../99
    0.575757...=57/99
    0.575757...=19/33

    The fraction 1933 is equivalent to 0.57. Thus, 0.57 fulfills the definition of a rational number, because it can be expressed as a fraction in the form ab, where a and b are integers and b≠ 0.