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Finding the Fourth Proportional to 208.70, 312.78 and 86.88

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Solution

The fourth proportional to 208.70, 312.78 and 86.88 is: 130.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.70 : 312.78 = 86.88 : x
  2. Step 2: Convert to fraction form
    208.70/312.78 = 86.88/x
  3. Step 3: Cross multiply
    208.70x = 312.78 × 86.88
  4. Step 4: Simplify right side
    208.70x = 27,174.33
  5. Step 5: Solve for x
    x = 27,174.33/208.70
  6. Step 6: Final answer
    x = 130.21

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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.