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Finding the Fourth Proportional to 128.13, 192.05 and 76.78

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Solution

The fourth proportional to 128.13, 192.05 and 76.78 is: 115.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.13 : 192.05 = 76.78 : x
  2. Step 2: Convert to fraction form
    128.13/192.05 = 76.78/x
  3. Step 3: Cross multiply
    128.13x = 192.05 × 76.78
  4. Step 4: Simplify right side
    128.13x = 14,745.60
  5. Step 5: Solve for x
    x = 14,745.60/128.13
  6. Step 6: Final answer
    x = 115.09

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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.