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Finding the Fourth Proportional to 208.61, 312.78 and 86.91

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Solution

The fourth proportional to 208.61, 312.78 and 86.91 is: 130.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.61 : 312.78 = 86.91 : x
  2. Step 2: Convert to fraction form
    208.61/312.78 = 86.91/x
  3. Step 3: Cross multiply
    208.61x = 312.78 × 86.91
  4. Step 4: Simplify right side
    208.61x = 27,183.71
  5. Step 5: Solve for x
    x = 27,183.71/208.61
  6. Step 6: Final answer
    x = 130.31

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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.