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Finding the Fourth Proportional to 138.57, 191.21 and 86.15

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Solution

The fourth proportional to 138.57, 191.21 and 86.15 is: 118.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.57 : 191.21 = 86.15 : x
  2. Step 2: Convert to fraction form
    138.57/191.21 = 86.15/x
  3. Step 3: Cross multiply
    138.57x = 191.21 × 86.15
  4. Step 4: Simplify right side
    138.57x = 16,471.35
  5. Step 5: Solve for x
    x = 16,471.35/138.57
  6. Step 6: Final answer
    x = 118.87

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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.