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Finding the Fourth Proportional to 128.42, 177.25 and 81.78

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Solution

The fourth proportional to 128.42, 177.25 and 81.78 is: 112.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.42 : 177.25 = 81.78 : x
  2. Step 2: Convert to fraction form
    128.42/177.25 = 81.78/x
  3. Step 3: Cross multiply
    128.42x = 177.25 × 81.78
  4. Step 4: Simplify right side
    128.42x = 14,495.99
  5. Step 5: Solve for x
    x = 14,495.99/128.42
  6. Step 6: Final answer
    x = 112.88

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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.