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Finding the Fourth Proportional to 128.54, 177.33 and 78.71

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Solution

The fourth proportional to 128.54, 177.33 and 78.71 is: 108.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.54 : 177.33 = 78.71 : x
  2. Step 2: Convert to fraction form
    128.54/177.33 = 78.71/x
  3. Step 3: Cross multiply
    128.54x = 177.33 × 78.71
  4. Step 4: Simplify right side
    128.54x = 13,956.36
  5. Step 5: Solve for x
    x = 13,956.36/128.54
  6. Step 6: Final answer
    x = 108.58

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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.