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Finding the Fourth Proportional to 20.72, 31.07 and 12.61

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Solution

The fourth proportional to 20.72, 31.07 and 12.61 is: 18.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.72 : 31.07 = 12.61 : x
  2. Step 2: Convert to fraction form
    20.72/31.07 = 12.61/x
  3. Step 3: Cross multiply
    20.72x = 31.07 × 12.61
  4. Step 4: Simplify right side
    20.72x = 391.79
  5. Step 5: Solve for x
    x = 391.79/20.72
  6. Step 6: Final answer
    x = 18.91

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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.