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Finding the Fourth Proportional to 639.74, 882.64 and 391

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Solution

The fourth proportional to 639.74, 882.64 and 391 is: 539.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.74 : 882.64 = 391 : x
  2. Step 2: Convert to fraction form
    639.74/882.64 = 391/x
  3. Step 3: Cross multiply
    639.74x = 882.64 × 391
  4. Step 4: Simplify right side
    639.74x = 345,112.24
  5. Step 5: Solve for x
    x = 345,112.24/639.74
  6. Step 6: Final answer
    x = 539.46

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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.