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Finding the Fourth Proportional to 208.64, 312.99 and 86.90

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Solution

The fourth proportional to 208.64, 312.99 and 86.90 is: 130.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.64 : 312.99 = 86.90 : x
  2. Step 2: Convert to fraction form
    208.64/312.99 = 86.90/x
  3. Step 3: Cross multiply
    208.64x = 312.99 × 86.90
  4. Step 4: Simplify right side
    208.64x = 27,198.83
  5. Step 5: Solve for x
    x = 27,198.83/208.64
  6. Step 6: Final answer
    x = 130.36

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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.