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Finding the Fourth Proportional to 781.42, 1,171.81 and 391.28

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Solution

The fourth proportional to 781.42, 1,171.81 and 391.28 is: 586.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.42 : 1,171.81 = 391.28 : x
  2. Step 2: Convert to fraction form
    781.42/1,171.81 = 391.28/x
  3. Step 3: Cross multiply
    781.42x = 1,171.81 × 391.28
  4. Step 4: Simplify right side
    781.42x = 458,498.98
  5. Step 5: Solve for x
    x = 458,498.98/781.42
  6. Step 6: Final answer
    x = 586.75

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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.