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Finding the Fourth Proportional to 208.07, 311.90 and 86.21

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Solution

The fourth proportional to 208.07, 311.90 and 86.21 is: 129.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.07 : 311.90 = 86.21 : x
  2. Step 2: Convert to fraction form
    208.07/311.90 = 86.21/x
  3. Step 3: Cross multiply
    208.07x = 311.90 × 86.21
  4. Step 4: Simplify right side
    208.07x = 26,890.32
  5. Step 5: Solve for x
    x = 26,890.32/208.07
  6. Step 6: Final answer
    x = 129.24

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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.