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Finding the Fourth Proportional to 81.48, 111.75 and 78.17

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Solution

The fourth proportional to 81.48, 111.75 and 78.17 is: 107.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.48 : 111.75 = 78.17 : x
  2. Step 2: Convert to fraction form
    81.48/111.75 = 78.17/x
  3. Step 3: Cross multiply
    81.48x = 111.75 × 78.17
  4. Step 4: Simplify right side
    81.48x = 8,735.11
  5. Step 5: Solve for x
    x = 8,735.11/81.48
  6. Step 6: Final answer
    x = 107.21

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.