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Finding the Fourth Proportional to 87.72, 121.61 and 84.30

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Solution

The fourth proportional to 87.72, 121.61 and 84.30 is: 116.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.72 : 121.61 = 84.30 : x
  2. Step 2: Convert to fraction form
    87.72/121.61 = 84.30/x
  3. Step 3: Cross multiply
    87.72x = 121.61 × 84.30
  4. Step 4: Simplify right side
    87.72x = 10,251.30
  5. Step 5: Solve for x
    x = 10,251.30/87.72
  6. Step 6: Final answer
    x = 116.86

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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.