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Finding the Fourth Proportional to 208.40, 312.39 and 86.49

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Solution

The fourth proportional to 208.40, 312.39 and 86.49 is: 129.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.40 : 312.39 = 86.49 : x
  2. Step 2: Convert to fraction form
    208.40/312.39 = 86.49/x
  3. Step 3: Cross multiply
    208.40x = 312.39 × 86.49
  4. Step 4: Simplify right side
    208.40x = 27,018.61
  5. Step 5: Solve for x
    x = 27,018.61/208.40
  6. Step 6: Final answer
    x = 129.65

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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.