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Finding the Fourth Proportional to 87.12, 120.47 and 78.12

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Solution

The fourth proportional to 87.12, 120.47 and 78.12 is: 108.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.12 : 120.47 = 78.12 : x
  2. Step 2: Convert to fraction form
    87.12/120.47 = 78.12/x
  3. Step 3: Cross multiply
    87.12x = 120.47 × 78.12
  4. Step 4: Simplify right side
    87.12x = 9,410.73
  5. Step 5: Solve for x
    x = 9,410.73/87.12
  6. Step 6: Final answer
    x = 108.02

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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.