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Finding the Fourth Proportional to 20.90, 31.28 and 11.88

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Solution

The fourth proportional to 20.90, 31.28 and 11.88 is: 17.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.90 : 31.28 = 11.88 : x
  2. Step 2: Convert to fraction form
    20.90/31.28 = 11.88/x
  3. Step 3: Cross multiply
    20.90x = 31.28 × 11.88
  4. Step 4: Simplify right side
    20.90x = 371.61
  5. Step 5: Solve for x
    x = 371.61/20.90
  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.