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Finding the Fourth Proportional to 128.90, 193.35 and 85.85

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Solution

The fourth proportional to 128.90, 193.35 and 85.85 is: 128.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.90 : 193.35 = 85.85 : x
  2. Step 2: Convert to fraction form
    128.90/193.35 = 85.85/x
  3. Step 3: Cross multiply
    128.90x = 193.35 × 85.85
  4. Step 4: Simplify right side
    128.90x = 16,599.10
  5. Step 5: Solve for x
    x = 16,599.10/128.90
  6. Step 6: Final answer
    x = 128.78

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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.