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Finding the Fourth Proportional to 128.71, 192.11 and 115.21

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Solution

The fourth proportional to 128.71, 192.11 and 115.21 is: 171.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.71 : 192.11 = 115.21 : x
  2. Step 2: Convert to fraction form
    128.71/192.11 = 115.21/x
  3. Step 3: Cross multiply
    128.71x = 192.11 × 115.21
  4. Step 4: Simplify right side
    128.71x = 22,132.99
  5. Step 5: Solve for x
    x = 22,132.99/128.71
  6. Step 6: Final answer
    x = 171.96

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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.