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Finding the Fourth Proportional to 87.58, 120.72 and 77.20

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Solution

The fourth proportional to 87.58, 120.72 and 77.20 is: 106.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.58 : 120.72 = 77.20 : x
  2. Step 2: Convert to fraction form
    87.58/120.72 = 77.20/x
  3. Step 3: Cross multiply
    87.58x = 120.72 × 77.20
  4. Step 4: Simplify right side
    87.58x = 9,320.25
  5. Step 5: Solve for x
    x = 9,320.25/87.58
  6. Step 6: Final answer
    x = 106.42

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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.