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Finding the Fourth Proportional to 100.78, 139.11 and 61.44

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Solution

The fourth proportional to 100.78, 139.11 and 61.44 is: 84.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.78 : 139.11 = 61.44 : x
  2. Step 2: Convert to fraction form
    100.78/139.11 = 61.44/x
  3. Step 3: Cross multiply
    100.78x = 139.11 × 61.44
  4. Step 4: Simplify right side
    100.78x = 8,546.92
  5. Step 5: Solve for x
    x = 8,546.92/100.78
  6. Step 6: Final answer
    x = 84.81

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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.