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Finding the Fourth Proportional to 81.20, 121.82 and 77.11

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Solution

The fourth proportional to 81.20, 121.82 and 77.11 is: 115.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.20 : 121.82 = 77.11 : x
  2. Step 2: Convert to fraction form
    81.20/121.82 = 77.11/x
  3. Step 3: Cross multiply
    81.20x = 121.82 × 77.11
  4. Step 4: Simplify right side
    81.20x = 9,392.85
  5. Step 5: Solve for x
    x = 9,392.85/81.20
  6. Step 6: Final answer
    x = 115.67

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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.