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Finding the Fourth Proportional to 128.78, 192.24 and 105.70

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Solution

The fourth proportional to 128.78, 192.24 and 105.70 is: 157.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.78 : 192.24 = 105.70 : x
  2. Step 2: Convert to fraction form
    128.78/192.24 = 105.70/x
  3. Step 3: Cross multiply
    128.78x = 192.24 × 105.70
  4. Step 4: Simplify right side
    128.78x = 20,319.77
  5. Step 5: Solve for x
    x = 20,319.77/128.78
  6. Step 6: Final answer
    x = 157.79

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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.