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Finding the Fourth Proportional to 20.92, 31.23 and 20.64

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Solution

The fourth proportional to 20.92, 31.23 and 20.64 is: 30.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.92 : 31.23 = 20.64 : x
  2. Step 2: Convert to fraction form
    20.92/31.23 = 20.64/x
  3. Step 3: Cross multiply
    20.92x = 31.23 × 20.64
  4. Step 4: Simplify right side
    20.92x = 644.59
  5. Step 5: Solve for x
    x = 644.59/20.92
  6. Step 6: Final answer
    x = 30.81

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.