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Finding the Fourth Proportional to 428.10, 591.39 and 391.20

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Solution

The fourth proportional to 428.10, 591.39 and 391.20 is: 540.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.10 : 591.39 = 391.20 : x
  2. Step 2: Convert to fraction form
    428.10/591.39 = 391.20/x
  3. Step 3: Cross multiply
    428.10x = 591.39 × 391.20
  4. Step 4: Simplify right side
    428.10x = 231,351.77
  5. Step 5: Solve for x
    x = 231,351.77/428.10
  6. Step 6: Final answer
    x = 540.42

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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.