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Finding the Fourth Proportional to 81.87, 123.38 and 72.78

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Solution

The fourth proportional to 81.87, 123.38 and 72.78 is: 109.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.87 : 123.38 = 72.78 : x
  2. Step 2: Convert to fraction form
    81.87/123.38 = 72.78/x
  3. Step 3: Cross multiply
    81.87x = 123.38 × 72.78
  4. Step 4: Simplify right side
    81.87x = 8,979.23
  5. Step 5: Solve for x
    x = 8,979.23/81.87
  6. Step 6: Final answer
    x = 109.68

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.