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Finding the Fourth Proportional to 31.86, 47.80 and 12.61

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Solution

The fourth proportional to 31.86, 47.80 and 12.61 is: 18.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.86 : 47.80 = 12.61 : x
  2. Step 2: Convert to fraction form
    31.86/47.80 = 12.61/x
  3. Step 3: Cross multiply
    31.86x = 47.80 × 12.61
  4. Step 4: Simplify right side
    31.86x = 602.88
  5. Step 5: Solve for x
    x = 602.88/31.86
  6. Step 6: Final answer
    x = 18.92

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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.