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Finding the Fourth Proportional to 639.77, 882.90 and 391.20

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Solution

The fourth proportional to 639.77, 882.90 and 391.20 is: 539.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.77 : 882.90 = 391.20 : x
  2. Step 2: Convert to fraction form
    639.77/882.90 = 391.20/x
  3. Step 3: Cross multiply
    639.77x = 882.90 × 391.20
  4. Step 4: Simplify right side
    639.77x = 345,387.17
  5. Step 5: Solve for x
    x = 345,387.17/639.77
  6. Step 6: Final answer
    x = 539.87

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