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Finding the Fourth Proportional to 678.72, 1,017.12 and 389.76

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Solution

The fourth proportional to 678.72, 1,017.12 and 389.76 is: 584.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.72 : 1,017.12 = 389.76 : x
  2. Step 2: Convert to fraction form
    678.72/1,017.12 = 389.76/x
  3. Step 3: Cross multiply
    678.72x = 1,017.12 × 389.76
  4. Step 4: Simplify right side
    678.72x = 396,432.69
  5. Step 5: Solve for x
    x = 396,432.69/678.72
  6. Step 6: Final answer
    x = 584.09

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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.