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Finding the Fourth Proportional to 128.47, 192.78 and 51.42

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Solution

The fourth proportional to 128.47, 192.78 and 51.42 is: 77.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.47 : 192.78 = 51.42 : x
  2. Step 2: Convert to fraction form
    128.47/192.78 = 51.42/x
  3. Step 3: Cross multiply
    128.47x = 192.78 × 51.42
  4. Step 4: Simplify right side
    128.47x = 9,912.75
  5. Step 5: Solve for x
    x = 9,912.75/128.47
  6. Step 6: Final answer
    x = 77.16

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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.