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Finding the Fourth Proportional to 8.61, 12.90 and 6.61

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Solution

The fourth proportional to 8.61, 12.90 and 6.61 is: 9.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    8.61 : 12.90 = 6.61 : x
  2. Step 2: Convert to fraction form
    8.61/12.90 = 6.61/x
  3. Step 3: Cross multiply
    8.61x = 12.90 × 6.61
  4. Step 4: Simplify right side
    8.61x = 85.27
  5. Step 5: Solve for x
    x = 85.27/8.61
  6. Step 6: Final answer
    x = 9.90

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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.