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Finding the Fourth Proportional to 13.89, 20.90 and 12.21

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Solution

The fourth proportional to 13.89, 20.90 and 12.21 is: 18.37

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.89 : 20.90 = 12.21 : x
  2. Step 2: Convert to fraction form
    13.89/20.90 = 12.21/x
  3. Step 3: Cross multiply
    13.89x = 20.90 × 12.21
  4. Step 4: Simplify right side
    13.89x = 255.13
  5. Step 5: Solve for x
    x = 255.13/13.89
  6. Step 6: Final answer
    x = 18.37

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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.