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Finding the Fourth Proportional to 13.57, 20.39 and 7.86

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Solution

The fourth proportional to 13.57, 20.39 and 7.86 is: 11.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.57 : 20.39 = 7.86 : x
  2. Step 2: Convert to fraction form
    13.57/20.39 = 7.86/x
  3. Step 3: Cross multiply
    13.57x = 20.39 × 7.86
  4. Step 4: Simplify right side
    13.57x = 160.31
  5. Step 5: Solve for x
    x = 160.31/13.57
  6. Step 6: Final answer
    x = 11.82

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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.