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Finding the Fourth Proportional to 639.70, 882.80 and 391.15

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Solution

The fourth proportional to 639.70, 882.80 and 391.15 is: 539.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.70 : 882.80 = 391.15 : x
  2. Step 2: Convert to fraction form
    639.70/882.80 = 391.15/x
  3. Step 3: Cross multiply
    639.70x = 882.80 × 391.15
  4. Step 4: Simplify right side
    639.70x = 345,310.32
  5. Step 5: Solve for x
    x = 345,310.32/639.70
  6. Step 6: Final answer
    x = 539.80

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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.