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Finding the Fourth Proportional to 428.69, 642.87 and 255.39

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Solution

The fourth proportional to 428.69, 642.87 and 255.39 is: 382.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.69 : 642.87 = 255.39 : x
  2. Step 2: Convert to fraction form
    428.69/642.87 = 255.39/x
  3. Step 3: Cross multiply
    428.69x = 642.87 × 255.39
  4. Step 4: Simplify right side
    428.69x = 164,182.57
  5. Step 5: Solve for x
    x = 164,182.57/428.69
  6. Step 6: Final answer
    x = 382.99

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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.