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Finding the Fourth Proportional to 138.99, 191.81 and 80.78

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Solution

The fourth proportional to 138.99, 191.81 and 80.78 is: 111.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.99 : 191.81 = 80.78 : x
  2. Step 2: Convert to fraction form
    138.99/191.81 = 80.78/x
  3. Step 3: Cross multiply
    138.99x = 191.81 × 80.78
  4. Step 4: Simplify right side
    138.99x = 15,493.05
  5. Step 5: Solve for x
    x = 15,493.05/138.99
  6. Step 6: Final answer
    x = 111.47

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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.