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Finding the Fourth Proportional to 81.36, 121.16 and 77.85

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Solution

The fourth proportional to 81.36, 121.16 and 77.85 is: 115.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.36 : 121.16 = 77.85 : x
  2. Step 2: Convert to fraction form
    81.36/121.16 = 77.85/x
  3. Step 3: Cross multiply
    81.36x = 121.16 × 77.85
  4. Step 4: Simplify right side
    81.36x = 9,432.31
  5. Step 5: Solve for x
    x = 9,432.31/81.36
  6. Step 6: Final answer
    x = 115.93

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.