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Finding the Fourth Proportional to 87.78, 121.02 and 65.91

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Solution

The fourth proportional to 87.78, 121.02 and 65.91 is: 90.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.78 : 121.02 = 65.91 : x
  2. Step 2: Convert to fraction form
    87.78/121.02 = 65.91/x
  3. Step 3: Cross multiply
    87.78x = 121.02 × 65.91
  4. Step 4: Simplify right side
    87.78x = 7,976.43
  5. Step 5: Solve for x
    x = 7,976.43/87.78
  6. Step 6: Final answer
    x = 90.87

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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.