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Finding the Fourth Proportional to 101.78, 140.54 and 81.20

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Solution

The fourth proportional to 101.78, 140.54 and 81.20 is: 112.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    101.78 : 140.54 = 81.20 : x
  2. Step 2: Convert to fraction form
    101.78/140.54 = 81.20/x
  3. Step 3: Cross multiply
    101.78x = 140.54 × 81.20
  4. Step 4: Simplify right side
    101.78x = 11,411.85
  5. Step 5: Solve for x
    x = 11,411.85/101.78
  6. Step 6: Final answer
    x = 112.12

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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.