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Finding the Fourth Proportional to 87.12, 129.90 and 77.88

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Solution

The fourth proportional to 87.12, 129.90 and 77.88 is: 116.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.12 : 129.90 = 77.88 : x
  2. Step 2: Convert to fraction form
    87.12/129.90 = 77.88/x
  3. Step 3: Cross multiply
    87.12x = 129.90 × 77.88
  4. Step 4: Simplify right side
    87.12x = 10,116.61
  5. Step 5: Solve for x
    x = 10,116.61/87.12
  6. Step 6: Final answer
    x = 116.12

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.