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Finding the Fourth Proportional to 781.61, 1,171.86 and 391.33

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Solution

The fourth proportional to 781.61, 1,171.86 and 391.33 is: 586.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.61 : 1,171.86 = 391.33 : x
  2. Step 2: Convert to fraction form
    781.61/1,171.86 = 391.33/x
  3. Step 3: Cross multiply
    781.61x = 1,171.86 × 391.33
  4. Step 4: Simplify right side
    781.61x = 458,586.17
  5. Step 5: Solve for x
    x = 458,586.17/781.61
  6. Step 6: Final answer
    x = 586.72

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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.