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Finding the Fourth Proportional to 87.87, 121.15 and 72.31

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Solution

The fourth proportional to 87.87, 121.15 and 72.31 is: 99.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.87 : 121.15 = 72.31 : x
  2. Step 2: Convert to fraction form
    87.87/121.15 = 72.31/x
  3. Step 3: Cross multiply
    87.87x = 121.15 × 72.31
  4. Step 4: Simplify right side
    87.87x = 8,760.36
  5. Step 5: Solve for x
    x = 8,760.36/87.87
  6. Step 6: Final answer
    x = 99.70

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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.