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Finding the Fourth Proportional to 128.81, 177.70 and 79.61

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Solution

The fourth proportional to 128.81, 177.70 and 79.61 is: 109.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.81 : 177.70 = 79.61 : x
  2. Step 2: Convert to fraction form
    128.81/177.70 = 79.61/x
  3. Step 3: Cross multiply
    128.81x = 177.70 × 79.61
  4. Step 4: Simplify right side
    128.81x = 14,146.70
  5. Step 5: Solve for x
    x = 14,146.70/128.81
  6. Step 6: Final answer
    x = 109.83

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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.