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Finding the Fourth Proportional to 20.81, 31.39 and 19.90

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Solution

The fourth proportional to 20.81, 31.39 and 19.90 is: 30.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.81 : 31.39 = 19.90 : x
  2. Step 2: Convert to fraction form
    20.81/31.39 = 19.90/x
  3. Step 3: Cross multiply
    20.81x = 31.39 × 19.90
  4. Step 4: Simplify right side
    20.81x = 624.66
  5. Step 5: Solve for x
    x = 624.66/20.81
  6. Step 6: Final answer
    x = 30.02

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.