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Finding the Fourth Proportional to 13.69, 18.90 and 7.86

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Solution

The fourth proportional to 13.69, 18.90 and 7.86 is: 10.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.69 : 18.90 = 7.86 : x
  2. Step 2: Convert to fraction form
    13.69/18.90 = 7.86/x
  3. Step 3: Cross multiply
    13.69x = 18.90 × 7.86
  4. Step 4: Simplify right side
    13.69x = 148.62
  5. Step 5: Solve for x
    x = 148.62/13.69
  6. Step 6: Final answer
    x = 10.85

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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.