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Finding the Fourth Proportional to 208.13, 311.90 and 86.31

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Solution

The fourth proportional to 208.13, 311.90 and 86.31 is: 129.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.13 : 311.90 = 86.31 : x
  2. Step 2: Convert to fraction form
    208.13/311.90 = 86.31/x
  3. Step 3: Cross multiply
    208.13x = 311.90 × 86.31
  4. Step 4: Simplify right side
    208.13x = 26,919.66
  5. Step 5: Solve for x
    x = 26,919.66/208.13
  6. Step 6: Final answer
    x = 129.34

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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.