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Finding the Fourth Proportional to 639.20, 882.16 and 390.69

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Solution

The fourth proportional to 639.20, 882.16 and 390.69 is: 539.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.20 : 882.16 = 390.69 : x
  2. Step 2: Convert to fraction form
    639.20/882.16 = 390.69/x
  3. Step 3: Cross multiply
    639.20x = 882.16 × 390.69
  4. Step 4: Simplify right side
    639.20x = 344,650.11
  5. Step 5: Solve for x
    x = 344,650.11/639.20
  6. Step 6: Final answer
    x = 539.19

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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.