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Finding the Fourth Proportional to 31.86, 47.79 and 13.86

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Solution

The fourth proportional to 31.86, 47.79 and 13.86 is: 20.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.86 : 47.79 = 13.86 : x
  2. Step 2: Convert to fraction form
    31.86/47.79 = 13.86/x
  3. Step 3: Cross multiply
    31.86x = 47.79 × 13.86
  4. Step 4: Simplify right side
    31.86x = 662.37
  5. Step 5: Solve for x
    x = 662.37/31.86
  6. Step 6: Final answer
    x = 20.79

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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.