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Finding the Fourth Proportional to 789.28, 1,089.31 and 478.78

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Solution

The fourth proportional to 789.28, 1,089.31 and 478.78 is: 660.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    789.28 : 1,089.31 = 478.78 : x
  2. Step 2: Convert to fraction form
    789.28/1,089.31 = 478.78/x
  3. Step 3: Cross multiply
    789.28x = 1,089.31 × 478.78
  4. Step 4: Simplify right side
    789.28x = 521,535.92
  5. Step 5: Solve for x
    x = 521,535.92/789.28
  6. Step 6: Final answer
    x = 660.78

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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.