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Finding the Fourth Proportional to 128.16, 176.87 and 72.90

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Solution

The fourth proportional to 128.16, 176.87 and 72.90 is: 100.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.16 : 176.87 = 72.90 : x
  2. Step 2: Convert to fraction form
    128.16/176.87 = 72.90/x
  3. Step 3: Cross multiply
    128.16x = 176.87 × 72.90
  4. Step 4: Simplify right side
    128.16x = 12,893.82
  5. Step 5: Solve for x
    x = 12,893.82/128.16
  6. Step 6: Final answer
    x = 100.61

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.