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Finding the Fourth Proportional to 13.89, 20.81 and 7.87

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Solution

The fourth proportional to 13.89, 20.81 and 7.87 is: 11.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.89 : 20.81 = 7.87 : x
  2. Step 2: Convert to fraction form
    13.89/20.81 = 7.87/x
  3. Step 3: Cross multiply
    13.89x = 20.81 × 7.87
  4. Step 4: Simplify right side
    13.89x = 163.77
  5. Step 5: Solve for x
    x = 163.77/13.89
  6. Step 6: Final answer
    x = 11.79

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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.