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Finding the Fourth Proportional to 81.90, 113.28 and 77.64

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Solution

The fourth proportional to 81.90, 113.28 and 77.64 is: 107.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.90 : 113.28 = 77.64 : x
  2. Step 2: Convert to fraction form
    81.90/113.28 = 77.64/x
  3. Step 3: Cross multiply
    81.90x = 113.28 × 77.64
  4. Step 4: Simplify right side
    81.90x = 8,795.06
  5. Step 5: Solve for x
    x = 8,795.06/81.90
  6. Step 6: Final answer
    x = 107.39

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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.