Big Ideas Math: Modeling Real Life, Grade 8
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5. Irrational Numbers
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Exercise 2 Page 406

Assign a variable to represent the repeating decimal. Then, write an equation by setting the variable and the decimal equal to each other.

1 130

Practice makes perfect

We want to write the given repeating decimal number as a mixed number. 1.03 To do so, we will follow six steps.

  1. Assign a variable to represent the repeating decimal.
  2. Write an equation by setting the variable and the decimal equal to each other.
  3. Multiply both sides of the equation by 10^d, where d is the number of repeating digits in the repeating decimal.
  4. Subtract equivalent expressions of the variable and the repeating decimal from each side of the equation.
  5. Solve for the variable. If necessary, write an equivalent fraction so that the numerator and denominator are integers.
  6. Write the obtained improper fraction as a mixed number.

    Let's do it!

    Steps 1 and 2

    Let's use the variable x to represent the given repeating decimal number. We can write an equation by setting this variable equal to 1.03. x=1.03

    Step 3

    Since the given number has one repeating digit, we will multiply both sides of the equation by 10^1.
    x=1.03
    x* 10^1=1.03* 10^1
    x* 10=1.03* 10
    10x=10.33

    Step 4

    We will now subtract x from both sides of the equation. Since x=1.03, we will substitute 1.03 for x on the right-hand side.
    10x=10.33
    10x-x=10.33-x
    10x-x=10.33- 1.03
    9x=9.3

    Step 5

    Next, we will solve the obtained equation for x.
    9x=9.3
    9x/9=9.3/9
    9x/9=9.3/9
    x=9.3/9

    Step 6

    Finally, we will write the obtained improper fraction as a mixed number. To do this, we will start by expressing the numerator as a sum.
    x=9.3/9
    x=9+0.3/9
    x=9/9+0.3/9
    x=1+0.3/9
    x=1+0.3* 10/9* 10
    x=1+3/90
    x=1+1/30
    x=1 130
    We found that x is equal to 1 130. Remember that x is also equal to 1.03. Therefore, the Transitive Property of Equality tells us that the fraction that we obtained is equal to the given repeating decimal number. x= 1.03 x= 1 130 ⇒ 1.03= 1 130