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Finding the Fourth Proportional to 13.86, 20.80 and 5.31

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Solution

The fourth proportional to 13.86, 20.80 and 5.31 is: 7.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.86 : 20.80 = 5.31 : x
  2. Step 2: Convert to fraction form
    13.86/20.80 = 5.31/x
  3. Step 3: Cross multiply
    13.86x = 20.80 × 5.31
  4. Step 4: Simplify right side
    13.86x = 110.45
  5. Step 5: Solve for x
    x = 110.45/13.86
  6. Step 6: Final answer
    x = 7.97

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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.