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Finding the Fourth Proportional to 87.72, 120.80 and 85.10

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Solution

The fourth proportional to 87.72, 120.80 and 85.10 is: 117.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.72 : 120.80 = 85.10 : x
  2. Step 2: Convert to fraction form
    87.72/120.80 = 85.10/x
  3. Step 3: Cross multiply
    87.72x = 120.80 × 85.10
  4. Step 4: Simplify right side
    87.72x = 10,279.05
  5. Step 5: Solve for x
    x = 10,279.05/87.72
  6. Step 6: Final answer
    x = 117.18

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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.