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Finding the Fourth Proportional to 21.77, 30.21 and 20.69

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Solution

The fourth proportional to 21.77, 30.21 and 20.69 is: 28.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.77 : 30.21 = 20.69 : x
  2. Step 2: Convert to fraction form
    21.77/30.21 = 20.69/x
  3. Step 3: Cross multiply
    21.77x = 30.21 × 20.69
  4. Step 4: Simplify right side
    21.77x = 624.93
  5. Step 5: Solve for x
    x = 624.93/21.77
  6. Step 6: Final answer
    x = 28.71

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.