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Finding the Fourth Proportional to 20.89, 31.31 and 11.86

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Solution

The fourth proportional to 20.89, 31.31 and 11.86 is: 17.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.89 : 31.31 = 11.86 : x
  2. Step 2: Convert to fraction form
    20.89/31.31 = 11.86/x
  3. Step 3: Cross multiply
    20.89x = 31.31 × 11.86
  4. Step 4: Simplify right side
    20.89x = 371.34
  5. Step 5: Solve for x
    x = 371.34/20.89
  6. Step 6: Final answer
    x = 17.78

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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.