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Finding the Fourth Proportional to 20.86, 31.31 and 18.47

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Solution

The fourth proportional to 20.86, 31.31 and 18.47 is: 27.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.86 : 31.31 = 18.47 : x
  2. Step 2: Convert to fraction form
    20.86/31.31 = 18.47/x
  3. Step 3: Cross multiply
    20.86x = 31.31 × 18.47
  4. Step 4: Simplify right side
    20.86x = 578.31
  5. Step 5: Solve for x
    x = 578.31/20.86
  6. Step 6: Final answer
    x = 27.72

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.