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Finding the Fourth Proportional to 128.82, 177.89 and 87.47

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Solution

The fourth proportional to 128.82, 177.89 and 87.47 is: 120.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.82 : 177.89 = 87.47 : x
  2. Step 2: Convert to fraction form
    128.82/177.89 = 87.47/x
  3. Step 3: Cross multiply
    128.82x = 177.89 × 87.47
  4. Step 4: Simplify right side
    128.82x = 15,558.71
  5. Step 5: Solve for x
    x = 15,558.71/128.82
  6. Step 6: Final answer
    x = 120.78

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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.