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Finding the Fourth Proportional to 213.72, 320.70 and 85.56

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Solution

The fourth proportional to 213.72, 320.70 and 85.56 is: 128.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    213.72 : 320.70 = 85.56 : x
  2. Step 2: Convert to fraction form
    213.72/320.70 = 85.56/x
  3. Step 3: Cross multiply
    213.72x = 320.70 × 85.56
  4. Step 4: Simplify right side
    213.72x = 27,439.09
  5. Step 5: Solve for x
    x = 27,439.09/213.72
  6. Step 6: Final answer
    x = 128.39

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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.