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Finding the Fourth Proportional to 128.12, 191.98 and 76.66

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Solution

The fourth proportional to 128.12, 191.98 and 76.66 is: 114.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.12 : 191.98 = 76.66 : x
  2. Step 2: Convert to fraction form
    128.12/191.98 = 76.66/x
  3. Step 3: Cross multiply
    128.12x = 191.98 × 76.66
  4. Step 4: Simplify right side
    128.12x = 14,716.52
  5. Step 5: Solve for x
    x = 14,716.52/128.12
  6. Step 6: Final answer
    x = 114.87

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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.