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Finding the Fourth Proportional to 8.61, 12.89 and 5.21

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Solution

The fourth proportional to 8.61, 12.89 and 5.21 is: 7.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    8.61 : 12.89 = 5.21 : x
  2. Step 2: Convert to fraction form
    8.61/12.89 = 5.21/x
  3. Step 3: Cross multiply
    8.61x = 12.89 × 5.21
  4. Step 4: Simplify right side
    8.61x = 67.21
  5. Step 5: Solve for x
    x = 67.21/8.61
  6. Step 6: Final answer
    x = 7.81

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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.