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Finding the Fourth Proportional to 87.12, 129.90 and 85.50

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Solution

The fourth proportional to 87.12, 129.90 and 85.50 is: 127.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.12 : 129.90 = 85.50 : x
  2. Step 2: Convert to fraction form
    87.12/129.90 = 85.50/x
  3. Step 3: Cross multiply
    87.12x = 129.90 × 85.50
  4. Step 4: Simplify right side
    87.12x = 11,106.45
  5. Step 5: Solve for x
    x = 11,106.45/87.12
  6. Step 6: Final answer
    x = 127.48

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.