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Finding the Fourth Proportional to 87.20, 120.40 and 76.40

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Solution

The fourth proportional to 87.20, 120.40 and 76.40 is: 105.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.20 : 120.40 = 76.40 : x
  2. Step 2: Convert to fraction form
    87.20/120.40 = 76.40/x
  3. Step 3: Cross multiply
    87.20x = 120.40 × 76.40
  4. Step 4: Simplify right side
    87.20x = 9,198.56
  5. Step 5: Solve for x
    x = 9,198.56/87.20
  6. Step 6: Final answer
    x = 105.49

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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.