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Finding the Fourth Proportional to 20.72, 28.61 and 15.86

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Solution

The fourth proportional to 20.72, 28.61 and 15.86 is: 21.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.72 : 28.61 = 15.86 : x
  2. Step 2: Convert to fraction form
    20.72/28.61 = 15.86/x
  3. Step 3: Cross multiply
    20.72x = 28.61 × 15.86
  4. Step 4: Simplify right side
    20.72x = 453.75
  5. Step 5: Solve for x
    x = 453.75/20.72
  6. Step 6: Final answer
    x = 21.90

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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.