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Finding the Fourth Proportional to 21.31, 31.81 and 18.61

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Solution

The fourth proportional to 21.31, 31.81 and 18.61 is: 27.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.31 : 31.81 = 18.61 : x
  2. Step 2: Convert to fraction form
    21.31/31.81 = 18.61/x
  3. Step 3: Cross multiply
    21.31x = 31.81 × 18.61
  4. Step 4: Simplify right side
    21.31x = 591.98
  5. Step 5: Solve for x
    x = 591.98/21.31
  6. Step 6: Final answer
    x = 27.78

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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.