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Finding the Fourth Proportional to 138.78, 191.43 and 86.94

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Solution

The fourth proportional to 138.78, 191.43 and 86.94 is: 119.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.78 : 191.43 = 86.94 : x
  2. Step 2: Convert to fraction form
    138.78/191.43 = 86.94/x
  3. Step 3: Cross multiply
    138.78x = 191.43 × 86.94
  4. Step 4: Simplify right side
    138.78x = 16,642.92
  5. Step 5: Solve for x
    x = 16,642.92/138.78
  6. Step 6: Final answer
    x = 119.92

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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.