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Finding the Fourth Proportional to 13.91, 20.87 and 8.57

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Solution

The fourth proportional to 13.91, 20.87 and 8.57 is: 12.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.91 : 20.87 = 8.57 : x
  2. Step 2: Convert to fraction form
    13.91/20.87 = 8.57/x
  3. Step 3: Cross multiply
    13.91x = 20.87 × 8.57
  4. Step 4: Simplify right side
    13.91x = 178.81
  5. Step 5: Solve for x
    x = 178.81/13.91
  6. Step 6: Final answer
    x = 12.86

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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.