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Finding the Fourth Proportional to 20.81, 28.68 and 15.91

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Solution

The fourth proportional to 20.81, 28.68 and 15.91 is: 21.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.81 : 28.68 = 15.91 : x
  2. Step 2: Convert to fraction form
    20.81/28.68 = 15.91/x
  3. Step 3: Cross multiply
    20.81x = 28.68 × 15.91
  4. Step 4: Simplify right side
    20.81x = 456.20
  5. Step 5: Solve for x
    x = 456.20/20.81
  6. Step 6: Final answer
    x = 21.93

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.