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Finding the Fourth Proportional to 201.20, 301.90 and 85.70

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Solution

The fourth proportional to 201.20, 301.90 and 85.70 is: 128.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    201.20 : 301.90 = 85.70 : x
  2. Step 2: Convert to fraction form
    201.20/301.90 = 85.70/x
  3. Step 3: Cross multiply
    201.20x = 301.90 × 85.70
  4. Step 4: Simplify right side
    201.20x = 25,872.83
  5. Step 5: Solve for x
    x = 25,872.83/201.20
  6. Step 6: Final answer
    x = 128.59

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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.