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Finding the Fourth Proportional to 206.78, 285.38 and 128.15

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Solution

The fourth proportional to 206.78, 285.38 and 128.15 is: 176.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    206.78 : 285.38 = 128.15 : x
  2. Step 2: Convert to fraction form
    206.78/285.38 = 128.15/x
  3. Step 3: Cross multiply
    206.78x = 285.38 × 128.15
  4. Step 4: Simplify right side
    206.78x = 36,569.38
  5. Step 5: Solve for x
    x = 36,569.38/206.78
  6. Step 6: Final answer
    x = 176.85

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.