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Finding the Fourth Proportional to 81.63, 121.89 and 69.48

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Solution

The fourth proportional to 81.63, 121.89 and 69.48 is: 103.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.63 : 121.89 = 69.48 : x
  2. Step 2: Convert to fraction form
    81.63/121.89 = 69.48/x
  3. Step 3: Cross multiply
    81.63x = 121.89 × 69.48
  4. Step 4: Simplify right side
    81.63x = 8,468.92
  5. Step 5: Solve for x
    x = 8,468.92/81.63
  6. Step 6: Final answer
    x = 103.75

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.