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Finding the Fourth Proportional to 128.25, 191.91 and 76.71

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Solution

The fourth proportional to 128.25, 191.91 and 76.71 is: 114.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.25 : 191.91 = 76.71 : x
  2. Step 2: Convert to fraction form
    128.25/191.91 = 76.71/x
  3. Step 3: Cross multiply
    128.25x = 191.91 × 76.71
  4. Step 4: Simplify right side
    128.25x = 14,721.42
  5. Step 5: Solve for x
    x = 14,721.42/128.25
  6. Step 6: Final answer
    x = 114.79

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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.