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Finding the Fourth Proportional to 128.70, 177.66 and 91.86

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Solution

The fourth proportional to 128.70, 177.66 and 91.86 is: 126.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.70 : 177.66 = 91.86 : x
  2. Step 2: Convert to fraction form
    128.70/177.66 = 91.86/x
  3. Step 3: Cross multiply
    128.70x = 177.66 × 91.86
  4. Step 4: Simplify right side
    128.70x = 16,319.85
  5. Step 5: Solve for x
    x = 16,319.85/128.70
  6. Step 6: Final answer
    x = 126.81

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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.