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Finding the Fourth Proportional to 128.98, 178.23 and 85.38

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Solution

The fourth proportional to 128.98, 178.23 and 85.38 is: 117.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.98 : 178.23 = 85.38 : x
  2. Step 2: Convert to fraction form
    128.98/178.23 = 85.38/x
  3. Step 3: Cross multiply
    128.98x = 178.23 × 85.38
  4. Step 4: Simplify right side
    128.98x = 15,217.28
  5. Step 5: Solve for x
    x = 15,217.28/128.98
  6. Step 6: Final answer
    x = 117.98

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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.