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Finding the Fourth Proportional to 21.71, 29.90 and 20.90

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Solution

The fourth proportional to 21.71, 29.90 and 20.90 is: 28.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.71 : 29.90 = 20.90 : x
  2. Step 2: Convert to fraction form
    21.71/29.90 = 20.90/x
  3. Step 3: Cross multiply
    21.71x = 29.90 × 20.90
  4. Step 4: Simplify right side
    21.71x = 624.91
  5. Step 5: Solve for x
    x = 624.91/21.71
  6. Step 6: Final answer
    x = 28.78

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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.