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Finding the Fourth Proportional to 86.70, 129.21 and 85.19

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Solution

The fourth proportional to 86.70, 129.21 and 85.19 is: 126.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.70 : 129.21 = 85.19 : x
  2. Step 2: Convert to fraction form
    86.70/129.21 = 85.19/x
  3. Step 3: Cross multiply
    86.70x = 129.21 × 85.19
  4. Step 4: Simplify right side
    86.70x = 11,006.75
  5. Step 5: Solve for x
    x = 11,006.75/86.70
  6. Step 6: Final answer
    x = 126.95

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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.