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Finding the Fourth Proportional to 20.42, 30.64 and 13.21

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Solution

The fourth proportional to 20.42, 30.64 and 13.21 is: 19.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.42 : 30.64 = 13.21 : x
  2. Step 2: Convert to fraction form
    20.42/30.64 = 13.21/x
  3. Step 3: Cross multiply
    20.42x = 30.64 × 13.21
  4. Step 4: Simplify right side
    20.42x = 404.60
  5. Step 5: Solve for x
    x = 404.60/20.42
  6. Step 6: Final answer
    x = 19.82

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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.