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Finding the Fourth Proportional to 87.80, 131.49 and 81.31

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Solution

The fourth proportional to 87.80, 131.49 and 81.31 is: 121.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.80 : 131.49 = 81.31 : x
  2. Step 2: Convert to fraction form
    87.80/131.49 = 81.31/x
  3. Step 3: Cross multiply
    87.80x = 131.49 × 81.31
  4. Step 4: Simplify right side
    87.80x = 10,690.79
  5. Step 5: Solve for x
    x = 10,690.79/87.80
  6. Step 6: Final answer
    x = 121.76

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.