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Finding the Fourth Proportional to 128.61, 177.49 and 78.82

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Solution

The fourth proportional to 128.61, 177.49 and 78.82 is: 108.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.61 : 177.49 = 78.82 : x
  2. Step 2: Convert to fraction form
    128.61/177.49 = 78.82/x
  3. Step 3: Cross multiply
    128.61x = 177.49 × 78.82
  4. Step 4: Simplify right side
    128.61x = 13,990.41
  5. Step 5: Solve for x
    x = 13,990.41/128.61
  6. Step 6: Final answer
    x = 108.78

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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.