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Finding the Fourth Proportional to 81.08, 111.91 and 78.51

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Solution

The fourth proportional to 81.08, 111.91 and 78.51 is: 108.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.08 : 111.91 = 78.51 : x
  2. Step 2: Convert to fraction form
    81.08/111.91 = 78.51/x
  3. Step 3: Cross multiply
    81.08x = 111.91 × 78.51
  4. Step 4: Simplify right side
    81.08x = 8,786.05
  5. Step 5: Solve for x
    x = 8,786.05/81.08
  6. Step 6: Final answer
    x = 108.36

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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.