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Finding the Fourth Proportional to 20.81, 31.21 and 7.28

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Solution

The fourth proportional to 20.81, 31.21 and 7.28 is: 10.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.81 : 31.21 = 7.28 : x
  2. Step 2: Convert to fraction form
    20.81/31.21 = 7.28/x
  3. Step 3: Cross multiply
    20.81x = 31.21 × 7.28
  4. Step 4: Simplify right side
    20.81x = 227.21
  5. Step 5: Solve for x
    x = 227.21/20.81
  6. Step 6: Final answer
    x = 10.92

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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.