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Finding the Fourth Proportional to 128.88, 177.86 and 85.30

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Solution

The fourth proportional to 128.88, 177.86 and 85.30 is: 117.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.88 : 177.86 = 85.30 : x
  2. Step 2: Convert to fraction form
    128.88/177.86 = 85.30/x
  3. Step 3: Cross multiply
    128.88x = 177.86 × 85.30
  4. Step 4: Simplify right side
    128.88x = 15,171.46
  5. Step 5: Solve for x
    x = 15,171.46/128.88
  6. Step 6: Final answer
    x = 117.72

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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.