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Finding the Fourth Proportional to 100.31, 138.39 and 81.86

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Solution

The fourth proportional to 100.31, 138.39 and 81.86 is: 112.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.31 : 138.39 = 81.86 : x
  2. Step 2: Convert to fraction form
    100.31/138.39 = 81.86/x
  3. Step 3: Cross multiply
    100.31x = 138.39 × 81.86
  4. Step 4: Simplify right side
    100.31x = 11,327.91
  5. Step 5: Solve for x
    x = 11,327.91/100.31
  6. Step 6: Final answer
    x = 112.93

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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.