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Finding the Fourth Proportional to 205.90, 309.11 and 128.68

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Solution

The fourth proportional to 205.90, 309.11 and 128.68 is: 193.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    205.90 : 309.11 = 128.68 : x
  2. Step 2: Convert to fraction form
    205.90/309.11 = 128.68/x
  3. Step 3: Cross multiply
    205.90x = 309.11 × 128.68
  4. Step 4: Simplify right side
    205.90x = 39,776.27
  5. Step 5: Solve for x
    x = 39,776.27/205.90
  6. Step 6: Final answer
    x = 193.18

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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.