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Finding the Fourth Proportional to 129.12, 193.56 and 85.80

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Solution

The fourth proportional to 129.12, 193.56 and 85.80 is: 128.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    129.12 : 193.56 = 85.80 : x
  2. Step 2: Convert to fraction form
    129.12/193.56 = 85.80/x
  3. Step 3: Cross multiply
    129.12x = 193.56 × 85.80
  4. Step 4: Simplify right side
    129.12x = 16,607.45
  5. Step 5: Solve for x
    x = 16,607.45/129.12
  6. Step 6: Final answer
    x = 128.62

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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.