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Finding the Fourth Proportional to 128.18, 192.21 and 45.90

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Solution

The fourth proportional to 128.18, 192.21 and 45.90 is: 68.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.18 : 192.21 = 45.90 : x
  2. Step 2: Convert to fraction form
    128.18/192.21 = 45.90/x
  3. Step 3: Cross multiply
    128.18x = 192.21 × 45.90
  4. Step 4: Simplify right side
    128.18x = 8,822.44
  5. Step 5: Solve for x
    x = 8,822.44/128.18
  6. Step 6: Final answer
    x = 68.83

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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.