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Finding the Fourth Proportional to 128.78, 192.01 and 120.11

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Solution

The fourth proportional to 128.78, 192.01 and 120.11 is: 179.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.78 : 192.01 = 120.11 : x
  2. Step 2: Convert to fraction form
    128.78/192.01 = 120.11/x
  3. Step 3: Cross multiply
    128.78x = 192.01 × 120.11
  4. Step 4: Simplify right side
    128.78x = 23,062.32
  5. Step 5: Solve for x
    x = 23,062.32/128.78
  6. Step 6: Final answer
    x = 179.08

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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.