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Finding the Fourth Proportional to 20.39, 30.40 and 18.87

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Solution

The fourth proportional to 20.39, 30.40 and 18.87 is: 28.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.39 : 30.40 = 18.87 : x
  2. Step 2: Convert to fraction form
    20.39/30.40 = 18.87/x
  3. Step 3: Cross multiply
    20.39x = 30.40 × 18.87
  4. Step 4: Simplify right side
    20.39x = 573.65
  5. Step 5: Solve for x
    x = 573.65/20.39
  6. Step 6: Final answer
    x = 28.13

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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.