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Finding the Fourth Proportional to 12.91, 17.80 and 8.61

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Solution

The fourth proportional to 12.91, 17.80 and 8.61 is: 11.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    12.91 : 17.80 = 8.61 : x
  2. Step 2: Convert to fraction form
    12.91/17.80 = 8.61/x
  3. Step 3: Cross multiply
    12.91x = 17.80 × 8.61
  4. Step 4: Simplify right side
    12.91x = 153.26
  5. Step 5: Solve for x
    x = 153.26/12.91
  6. Step 6: Final answer
    x = 11.87

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.