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Finding the Fourth Proportional to 21.40, 31.89 and 20.66

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Solution

The fourth proportional to 21.40, 31.89 and 20.66 is: 30.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.40 : 31.89 = 20.66 : x
  2. Step 2: Convert to fraction form
    21.40/31.89 = 20.66/x
  3. Step 3: Cross multiply
    21.40x = 31.89 × 20.66
  4. Step 4: Simplify right side
    21.40x = 658.64
  5. Step 5: Solve for x
    x = 658.64/21.40
  6. Step 6: Final answer
    x = 30.78

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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.