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Finding the Fourth Proportional to 7.91, 11.85 and 3.90

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Solution

The fourth proportional to 7.91, 11.85 and 3.90 is: 5.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    7.91 : 11.85 = 3.90 : x
  2. Step 2: Convert to fraction form
    7.91/11.85 = 3.90/x
  3. Step 3: Cross multiply
    7.91x = 11.85 × 3.90
  4. Step 4: Simplify right side
    7.91x = 46.22
  5. Step 5: Solve for x
    x = 46.22/7.91
  6. Step 6: Final answer
    x = 5.85

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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.