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Finding the Fourth Proportional to 221.21, 331.78 and 139.85

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Solution

The fourth proportional to 221.21, 331.78 and 139.85 is: 209.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.21 : 331.78 = 139.85 : x
  2. Step 2: Convert to fraction form
    221.21/331.78 = 139.85/x
  3. Step 3: Cross multiply
    221.21x = 331.78 × 139.85
  4. Step 4: Simplify right side
    221.21x = 46,399.43
  5. Step 5: Solve for x
    x = 46,399.43/221.21
  6. Step 6: Final answer
    x = 209.75

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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.