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Finding the Fourth Proportional to 81.40, 121.79 and 45.36

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Solution

The fourth proportional to 81.40, 121.79 and 45.36 is: 67.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.40 : 121.79 = 45.36 : x
  2. Step 2: Convert to fraction form
    81.40/121.79 = 45.36/x
  3. Step 3: Cross multiply
    81.40x = 121.79 × 45.36
  4. Step 4: Simplify right side
    81.40x = 5,524.39
  5. Step 5: Solve for x
    x = 5,524.39/81.40
  6. Step 6: Final answer
    x = 67.87

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.