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Finding the Fourth Proportional to 12.89, 19.31 and 7.80

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Solution

The fourth proportional to 12.89, 19.31 and 7.80 is: 11.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    12.89 : 19.31 = 7.80 : x
  2. Step 2: Convert to fraction form
    12.89/19.31 = 7.80/x
  3. Step 3: Cross multiply
    12.89x = 19.31 × 7.80
  4. Step 4: Simplify right side
    12.89x = 150.62
  5. Step 5: Solve for x
    x = 150.62/12.89
  6. Step 6: Final answer
    x = 11.68

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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.