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Finding the Fourth Proportional to 13.92, 20.80 and 12.31

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Solution

The fourth proportional to 13.92, 20.80 and 12.31 is: 18.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.92 : 20.80 = 12.31 : x
  2. Step 2: Convert to fraction form
    13.92/20.80 = 12.31/x
  3. Step 3: Cross multiply
    13.92x = 20.80 × 12.31
  4. Step 4: Simplify right side
    13.92x = 256.06
  5. Step 5: Solve for x
    x = 256.06/13.92
  6. Step 6: Final answer
    x = 18.40

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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.