Add & Subtract Rational Numbers Sample Work

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Sure! Let's go through some sample problems involving adding and subtracting rational numbers step by step.

Sample Problem 1: Adding Rational Numbers

Problem: Add \( \frac{3}{4} + \frac{5}{8} \).

Step 1: Find a common denominator. The denominators are 4 and 8. The least common denominator (LCD) is 8.

Step 2: Convert fractions to have the same denominator.

  • \( \frac{3}{4} = \frac{3 \times 2}{4 \times 2} = \frac{6}{8} \)
  • \( \frac{5}{8} \) already has the denominator of 8.

Step 3: Add the fractions. \[ \frac{6}{8} + \frac{5}{8} = \frac{6 + 5}{8} = \frac{11}{8} \]

Step 4: Simplify if necessary. \( \frac{11}{8} \) is an improper fraction, which can also be written as \( 1 \frac{3}{8} \).

Final Answer for Addition:

\[ \frac{3}{4} + \frac{5}{8} = \frac{11}{8} \text{ or } 1 \frac{3}{8} \]


Sample Problem 2: Subtracting Rational Numbers

Problem: Subtract \( \frac{7}{10} - \frac{1}{5} \).

Step 1: Find a common denominator. The denominators are 10 and 5. The least common denominator (LCD) is 10.

Step 2: Convert fractions to have the same denominator.

  • \( \frac{1}{5} = \frac{1 \times 2}{5 \times 2} = \frac{2}{10} \)

Step 3: Subtract the fractions. \[ \frac{7}{10} - \frac{2}{10} = \frac{7 - 2}{10} = \frac{5}{10} \]

Step 4: Simplify if necessary. \( \frac{5}{10} \) simplifies to \( \frac{1}{2} \).

Final Answer for Subtraction:

\[ \frac{7}{10} - \frac{1}{5} = \frac{1}{2} \]


Summary of Processes

  1. Adding:

    • Find a common denominator.
    • Convert fractions to that common denominator.
    • Add the numerators and keep the common denominator.
    • Simplify if possible.
  2. Subtracting:

    • Find a common denominator.
    • Convert fractions to that common denominator.
    • Subtract the numerators and keep the common denominator.
    • Simplify if possible.

These steps can be used for any addition and subtraction of rational numbers! If you'd like more practice problems or different examples, feel free to ask!