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Finding the Fourth Proportional to 128.78, 193.17 and 47.61

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Solution

The fourth proportional to 128.78, 193.17 and 47.61 is: 71.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.78 : 193.17 = 47.61 : x
  2. Step 2: Convert to fraction form
    128.78/193.17 = 47.61/x
  3. Step 3: Cross multiply
    128.78x = 193.17 × 47.61
  4. Step 4: Simplify right side
    128.78x = 9,196.82
  5. Step 5: Solve for x
    x = 9,196.82/128.78
  6. Step 6: Final answer
    x = 71.42

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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.