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Finding the Fourth Proportional to 213.61, 320.42 and 85.39

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Solution

The fourth proportional to 213.61, 320.42 and 85.39 is: 128.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    213.61 : 320.42 = 85.39 : x
  2. Step 2: Convert to fraction form
    213.61/320.42 = 85.39/x
  3. Step 3: Cross multiply
    213.61x = 320.42 × 85.39
  4. Step 4: Simplify right side
    213.61x = 27,360.66
  5. Step 5: Solve for x
    x = 27,360.66/213.61
  6. Step 6: Final answer
    x = 128.09

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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.