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Finding the Fourth Proportional to 20.65, 30.97 and 7.81

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Solution

The fourth proportional to 20.65, 30.97 and 7.81 is: 11.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.65 : 30.97 = 7.81 : x
  2. Step 2: Convert to fraction form
    20.65/30.97 = 7.81/x
  3. Step 3: Cross multiply
    20.65x = 30.97 × 7.81
  4. Step 4: Simplify right side
    20.65x = 241.88
  5. Step 5: Solve for x
    x = 241.88/20.65
  6. Step 6: Final answer
    x = 11.71

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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.