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Finding the Fourth Proportional to 31.81, 43.92 and 20.91

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Solution

The fourth proportional to 31.81, 43.92 and 20.91 is: 28.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.81 : 43.92 = 20.91 : x
  2. Step 2: Convert to fraction form
    31.81/43.92 = 20.91/x
  3. Step 3: Cross multiply
    31.81x = 43.92 × 20.91
  4. Step 4: Simplify right side
    31.81x = 918.26
  5. Step 5: Solve for x
    x = 918.26/31.81
  6. Step 6: Final answer
    x = 28.87

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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.