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Finding the Fourth Proportional to 128.24, 191.81 and 87.20

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Solution

The fourth proportional to 128.24, 191.81 and 87.20 is: 130.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.24 : 191.81 = 87.20 : x
  2. Step 2: Convert to fraction form
    128.24/191.81 = 87.20/x
  3. Step 3: Cross multiply
    128.24x = 191.81 × 87.20
  4. Step 4: Simplify right side
    128.24x = 16,724.87
  5. Step 5: Solve for x
    x = 16,724.87/128.24
  6. Step 6: Final answer
    x = 130.42

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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.