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Finding the Fourth Proportional to 20.74, 31.11 and 7.21

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Solution

The fourth proportional to 20.74, 31.11 and 7.21 is: 10.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.74 : 31.11 = 7.21 : x
  2. Step 2: Convert to fraction form
    20.74/31.11 = 7.21/x
  3. Step 3: Cross multiply
    20.74x = 31.11 × 7.21
  4. Step 4: Simplify right side
    20.74x = 224.27
  5. Step 5: Solve for x
    x = 224.27/20.74
  6. Step 6: Final answer
    x = 10.81

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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.