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Finding the Fourth Proportional to 639.80, 882.90 and 391.13

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Solution

The fourth proportional to 639.80, 882.90 and 391.13 is: 539.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.80 : 882.90 = 391.13 : x
  2. Step 2: Convert to fraction form
    639.80/882.90 = 391.13/x
  3. Step 3: Cross multiply
    639.80x = 882.90 × 391.13
  4. Step 4: Simplify right side
    639.80x = 345,327.57
  5. Step 5: Solve for x
    x = 345,327.57/639.80
  6. Step 6: Final answer
    x = 539.74

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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.