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Finding the Fourth Proportional to 80.91, 121.28 and 71.91

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Solution

The fourth proportional to 80.91, 121.28 and 71.91 is: 107.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    80.91 : 121.28 = 71.91 : x
  2. Step 2: Convert to fraction form
    80.91/121.28 = 71.91/x
  3. Step 3: Cross multiply
    80.91x = 121.28 × 71.91
  4. Step 4: Simplify right side
    80.91x = 8,720.89
  5. Step 5: Solve for x
    x = 8,720.89/80.91
  6. Step 6: Final answer
    x = 107.79

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.