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Finding the Fourth Proportional to 639.20, 882.12 and 390.63

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Solution

The fourth proportional to 639.20, 882.12 and 390.63 is: 539.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.20 : 882.12 = 390.63 : x
  2. Step 2: Convert to fraction form
    639.20/882.12 = 390.63/x
  3. Step 3: Cross multiply
    639.20x = 882.12 × 390.63
  4. Step 4: Simplify right side
    639.20x = 344,582.54
  5. Step 5: Solve for x
    x = 344,582.54/639.20
  6. Step 6: Final answer
    x = 539.08

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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.