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Finding the Fourth Proportional to 128.39, 191.41 and 120.65

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Solution

The fourth proportional to 128.39, 191.41 and 120.65 is: 179.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.39 : 191.41 = 120.65 : x
  2. Step 2: Convert to fraction form
    128.39/191.41 = 120.65/x
  3. Step 3: Cross multiply
    128.39x = 191.41 × 120.65
  4. Step 4: Simplify right side
    128.39x = 23,092.36
  5. Step 5: Solve for x
    x = 23,092.36/128.39
  6. Step 6: Final answer
    x = 179.87

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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.