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Finding the Fourth Proportional to 256.90, 385.30 and 85.90

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Solution

The fourth proportional to 256.90, 385.30 and 85.90 is: 128.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    256.90 : 385.30 = 85.90 : x
  2. Step 2: Convert to fraction form
    256.90/385.30 = 85.90/x
  3. Step 3: Cross multiply
    256.90x = 385.30 × 85.90
  4. Step 4: Simplify right side
    256.90x = 33,097.27
  5. Step 5: Solve for x
    x = 33,097.27/256.90
  6. Step 6: Final answer
    x = 128.83

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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.