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Finding the Fourth Proportional to 128.19, 192.39 and 87.12

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Solution

The fourth proportional to 128.19, 192.39 and 87.12 is: 130.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.19 : 192.39 = 87.12 : x
  2. Step 2: Convert to fraction form
    128.19/192.39 = 87.12/x
  3. Step 3: Cross multiply
    128.19x = 192.39 × 87.12
  4. Step 4: Simplify right side
    128.19x = 16,761.02
  5. Step 5: Solve for x
    x = 16,761.02/128.19
  6. Step 6: Final answer
    x = 130.75

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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.