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Finding the Fourth Proportional to 13.87, 20.81 and 7.78

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Solution

The fourth proportional to 13.87, 20.81 and 7.78 is: 11.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.87 : 20.81 = 7.78 : x
  2. Step 2: Convert to fraction form
    13.87/20.81 = 7.78/x
  3. Step 3: Cross multiply
    13.87x = 20.81 × 7.78
  4. Step 4: Simplify right side
    13.87x = 161.85
  5. Step 5: Solve for x
    x = 161.85/13.87
  6. Step 6: Final answer
    x = 11.67

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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.