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Finding the Fourth Proportional to 781.19, 1,171.31 and 391.30

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Solution

The fourth proportional to 781.19, 1,171.31 and 391.30 is: 586.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.19 : 1,171.31 = 391.30 : x
  2. Step 2: Convert to fraction form
    781.19/1,171.31 = 391.30/x
  3. Step 3: Cross multiply
    781.19x = 1,171.31 × 391.30
  4. Step 4: Simplify right side
    781.19x = 458,333.60
  5. Step 5: Solve for x
    x = 458,333.60/781.19
  6. Step 6: Final answer
    x = 586.71

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.