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Finding the Fourth Proportional to 138.90, 191.61 and 86.43

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Solution

The fourth proportional to 138.90, 191.61 and 86.43 is: 119.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.90 : 191.61 = 86.43 : x
  2. Step 2: Convert to fraction form
    138.90/191.61 = 86.43/x
  3. Step 3: Cross multiply
    138.90x = 191.61 × 86.43
  4. Step 4: Simplify right side
    138.90x = 16,560.49
  5. Step 5: Solve for x
    x = 16,560.49/138.90
  6. Step 6: Final answer
    x = 119.22

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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.