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Finding the Fourth Proportional to 86.10, 129 and 42.70

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Solution

The fourth proportional to 86.10, 129 and 42.70 is: 63.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.10 : 129 = 42.70 : x
  2. Step 2: Convert to fraction form
    86.10/129 = 42.70/x
  3. Step 3: Cross multiply
    86.10x = 129 × 42.70
  4. Step 4: Simplify right side
    86.10x = 5,508.30
  5. Step 5: Solve for x
    x = 5,508.30/86.10
  6. Step 6: Final answer
    x = 63.98

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.