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Finding the Fourth Proportional to 128.40, 192.72 and 92.40

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Solution

The fourth proportional to 128.40, 192.72 and 92.40 is: 138.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.40 : 192.72 = 92.40 : x
  2. Step 2: Convert to fraction form
    128.40/192.72 = 92.40/x
  3. Step 3: Cross multiply
    128.40x = 192.72 × 92.40
  4. Step 4: Simplify right side
    128.40x = 17,807.33
  5. Step 5: Solve for x
    x = 17,807.33/128.40
  6. Step 6: Final answer
    x = 138.69

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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.