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Finding the Fourth Proportional to 87.11, 129.81 and 84.21

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Solution

The fourth proportional to 87.11, 129.81 and 84.21 is: 125.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.11 : 129.81 = 84.21 : x
  2. Step 2: Convert to fraction form
    87.11/129.81 = 84.21/x
  3. Step 3: Cross multiply
    87.11x = 129.81 × 84.21
  4. Step 4: Simplify right side
    87.11x = 10,931.30
  5. Step 5: Solve for x
    x = 10,931.30/87.11
  6. Step 6: Final answer
    x = 125.49

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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.