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Finding the Fourth Proportional to 781.23, 1,171.72 and 391.11

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Solution

The fourth proportional to 781.23, 1,171.72 and 391.11 is: 586.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.23 : 1,171.72 = 391.11 : x
  2. Step 2: Convert to fraction form
    781.23/1,171.72 = 391.11/x
  3. Step 3: Cross multiply
    781.23x = 1,171.72 × 391.11
  4. Step 4: Simplify right side
    781.23x = 458,271.41
  5. Step 5: Solve for x
    x = 458,271.41/781.23
  6. Step 6: Final answer
    x = 586.60

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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.