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Finding the Fourth Proportional to 780.75, 1,171.17 and 390.85

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Solution

The fourth proportional to 780.75, 1,171.17 and 390.85 is: 586.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    780.75 : 1,171.17 = 390.85 : x
  2. Step 2: Convert to fraction form
    780.75/1,171.17 = 390.85/x
  3. Step 3: Cross multiply
    780.75x = 1,171.17 × 390.85
  4. Step 4: Simplify right side
    780.75x = 457,748.87
  5. Step 5: Solve for x
    x = 457,748.87/780.75
  6. Step 6: Final answer
    x = 586.29

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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.