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Finding the Fourth Proportional to 128.15, 176.84 and 72.90

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Solution

The fourth proportional to 128.15, 176.84 and 72.90 is: 100.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.15 : 176.84 = 72.90 : x
  2. Step 2: Convert to fraction form
    128.15/176.84 = 72.90/x
  3. Step 3: Cross multiply
    128.15x = 176.84 × 72.90
  4. Step 4: Simplify right side
    128.15x = 12,891.45
  5. Step 5: Solve for x
    x = 12,891.45/128.15
  6. Step 6: Final answer
    x = 100.60

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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.