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Finding the Fourth Proportional to 20.90, 31.29 and 13.29

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Solution

The fourth proportional to 20.90, 31.29 and 13.29 is: 19.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.90 : 31.29 = 13.29 : x
  2. Step 2: Convert to fraction form
    20.90/31.29 = 13.29/x
  3. Step 3: Cross multiply
    20.90x = 31.29 × 13.29
  4. Step 4: Simplify right side
    20.90x = 415.73
  5. Step 5: Solve for x
    x = 415.73/20.90
  6. Step 6: Final answer
    x = 19.89

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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.