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Finding the Fourth Proportional to 128.14, 176.78 and 86.70

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Solution

The fourth proportional to 128.14, 176.78 and 86.70 is: 119.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.14 : 176.78 = 86.70 : x
  2. Step 2: Convert to fraction form
    128.14/176.78 = 86.70/x
  3. Step 3: Cross multiply
    128.14x = 176.78 × 86.70
  4. Step 4: Simplify right side
    128.14x = 15,326.83
  5. Step 5: Solve for x
    x = 15,326.83/128.14
  6. Step 6: Final answer
    x = 119.61

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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.