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Finding the Fourth Proportional to 81.30, 121.65 and 76.86

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Solution

The fourth proportional to 81.30, 121.65 and 76.86 is: 115.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.30 : 121.65 = 76.86 : x
  2. Step 2: Convert to fraction form
    81.30/121.65 = 76.86/x
  3. Step 3: Cross multiply
    81.30x = 121.65 × 76.86
  4. Step 4: Simplify right side
    81.30x = 9,350.02
  5. Step 5: Solve for x
    x = 9,350.02/81.30
  6. Step 6: Final answer
    x = 115.01

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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.