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Finding the Fourth Proportional to 87.61, 121.13 and 83.78

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Solution

The fourth proportional to 87.61, 121.13 and 83.78 is: 115.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.61 : 121.13 = 83.78 : x
  2. Step 2: Convert to fraction form
    87.61/121.13 = 83.78/x
  3. Step 3: Cross multiply
    87.61x = 121.13 × 83.78
  4. Step 4: Simplify right side
    87.61x = 10,148.70
  5. Step 5: Solve for x
    x = 10,148.70/87.61
  6. Step 6: Final answer
    x = 115.84

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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.