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Finding the Fourth Proportional to 639.78, 882.47 and 390.92

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Solution

The fourth proportional to 639.78, 882.47 and 390.92 is: 539.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.78 : 882.47 = 390.92 : x
  2. Step 2: Convert to fraction form
    639.78/882.47 = 390.92/x
  3. Step 3: Cross multiply
    639.78x = 882.47 × 390.92
  4. Step 4: Simplify right side
    639.78x = 344,968.81
  5. Step 5: Solve for x
    x = 344,968.81/639.78
  6. Step 6: Final answer
    x = 539.20

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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.