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Finding the Fourth Proportional to 87.20, 130.80 and 86.60

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Solution

The fourth proportional to 87.20, 130.80 and 86.60 is: 129.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.20 : 130.80 = 86.60 : x
  2. Step 2: Convert to fraction form
    87.20/130.80 = 86.60/x
  3. Step 3: Cross multiply
    87.20x = 130.80 × 86.60
  4. Step 4: Simplify right side
    87.20x = 11,327.28
  5. Step 5: Solve for x
    x = 11,327.28/87.20
  6. Step 6: Final answer
    x = 129.90

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.