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Finding the Fourth Proportional to 81.60, 112.59 and 78.09

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Solution

The fourth proportional to 81.60, 112.59 and 78.09 is: 107.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.60 : 112.59 = 78.09 : x
  2. Step 2: Convert to fraction form
    81.60/112.59 = 78.09/x
  3. Step 3: Cross multiply
    81.60x = 112.59 × 78.09
  4. Step 4: Simplify right side
    81.60x = 8,792.15
  5. Step 5: Solve for x
    x = 8,792.15/81.60
  6. Step 6: Final answer
    x = 107.75

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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.