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Finding the Fourth Proportional to 128.28, 191.16 and 120

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Solution

The fourth proportional to 128.28, 191.16 and 120 is: 178.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.28 : 191.16 = 120 : x
  2. Step 2: Convert to fraction form
    128.28/191.16 = 120/x
  3. Step 3: Cross multiply
    128.28x = 191.16 × 120
  4. Step 4: Simplify right side
    128.28x = 22,939.20
  5. Step 5: Solve for x
    x = 22,939.20/128.28
  6. Step 6: Final answer
    x = 178.82

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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.