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Finding the Fourth Proportional to 391.20, 587.15 and 318.90

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Solution

The fourth proportional to 391.20, 587.15 and 318.90 is: 478.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    391.20 : 587.15 = 318.90 : x
  2. Step 2: Convert to fraction form
    391.20/587.15 = 318.90/x
  3. Step 3: Cross multiply
    391.20x = 587.15 × 318.90
  4. Step 4: Simplify right side
    391.20x = 187,243.94
  5. Step 5: Solve for x
    x = 187,243.94/391.20
  6. Step 6: Final answer
    x = 478.64

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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.