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Finding the Fourth Proportional to 851.78, 1,278.05 and 389.61

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Solution

The fourth proportional to 851.78, 1,278.05 and 389.61 is: 584.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    851.78 : 1,278.05 = 389.61 : x
  2. Step 2: Convert to fraction form
    851.78/1,278.05 = 389.61/x
  3. Step 3: Cross multiply
    851.78x = 1,278.05 × 389.61
  4. Step 4: Simplify right side
    851.78x = 497,939.11
  5. Step 5: Solve for x
    x = 497,939.11/851.78
  6. Step 6: Final answer
    x = 584.58

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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.