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Finding the Fourth Proportional to 86.70, 129.35 and 86.09

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Solution

The fourth proportional to 86.70, 129.35 and 86.09 is: 128.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.70 : 129.35 = 86.09 : x
  2. Step 2: Convert to fraction form
    86.70/129.35 = 86.09/x
  3. Step 3: Cross multiply
    86.70x = 129.35 × 86.09
  4. Step 4: Simplify right side
    86.70x = 11,134.66
  5. Step 5: Solve for x
    x = 11,134.66/86.70
  6. Step 6: Final answer
    x = 128.43

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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.