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Finding the Fourth Proportional to 87.90, 121.97 and 85.38

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Solution

The fourth proportional to 87.90, 121.97 and 85.38 is: 118.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.90 : 121.97 = 85.38 : x
  2. Step 2: Convert to fraction form
    87.90/121.97 = 85.38/x
  3. Step 3: Cross multiply
    87.90x = 121.97 × 85.38
  4. Step 4: Simplify right side
    87.90x = 10,413.37
  5. Step 5: Solve for x
    x = 10,413.37/87.90
  6. Step 6: Final answer
    x = 118.47

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.