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Finding the Fourth Proportional to 639.78, 882.90 and 391.02

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Solution

The fourth proportional to 639.78, 882.90 and 391.02 is: 539.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.78 : 882.90 = 391.02 : x
  2. Step 2: Convert to fraction form
    639.78/882.90 = 391.02/x
  3. Step 3: Cross multiply
    639.78x = 882.90 × 391.02
  4. Step 4: Simplify right side
    639.78x = 345,231.56
  5. Step 5: Solve for x
    x = 345,231.56/639.78
  6. Step 6: Final answer
    x = 539.61

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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.