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Finding the Fourth Proportional to 20.90, 28.85 and 13.61

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Solution

The fourth proportional to 20.90, 28.85 and 13.61 is: 18.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.90 : 28.85 = 13.61 : x
  2. Step 2: Convert to fraction form
    20.90/28.85 = 13.61/x
  3. Step 3: Cross multiply
    20.90x = 28.85 × 13.61
  4. Step 4: Simplify right side
    20.90x = 392.65
  5. Step 5: Solve for x
    x = 392.65/20.90
  6. Step 6: Final answer
    x = 18.78

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.