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Finding the Fourth Proportional to 20.91, 31.12 and 20.85

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Solution

The fourth proportional to 20.91, 31.12 and 20.85 is: 31.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.91 : 31.12 = 20.85 : x
  2. Step 2: Convert to fraction form
    20.91/31.12 = 20.85/x
  3. Step 3: Cross multiply
    20.91x = 31.12 × 20.85
  4. Step 4: Simplify right side
    20.91x = 648.85
  5. Step 5: Solve for x
    x = 648.85/20.91
  6. Step 6: Final answer
    x = 31.03

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.