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Finding the Fourth Proportional to 428.28, 638.77 and 391.84

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Solution

The fourth proportional to 428.28, 638.77 and 391.84 is: 584.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.28 : 638.77 = 391.84 : x
  2. Step 2: Convert to fraction form
    428.28/638.77 = 391.84/x
  3. Step 3: Cross multiply
    428.28x = 638.77 × 391.84
  4. Step 4: Simplify right side
    428.28x = 250,295.64
  5. Step 5: Solve for x
    x = 250,295.64/428.28
  6. Step 6: Final answer
    x = 584.42

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.