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Finding the Fourth Proportional to 208.58, 312.91 and 86.85

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Solution

The fourth proportional to 208.58, 312.91 and 86.85 is: 130.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.58 : 312.91 = 86.85 : x
  2. Step 2: Convert to fraction form
    208.58/312.91 = 86.85/x
  3. Step 3: Cross multiply
    208.58x = 312.91 × 86.85
  4. Step 4: Simplify right side
    208.58x = 27,176.02
  5. Step 5: Solve for x
    x = 27,176.02/208.58
  6. Step 6: Final answer
    x = 130.29

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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.