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Finding the Fourth Proportional to 20.45, 28.20 and 13.89

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Solution

The fourth proportional to 20.45, 28.20 and 13.89 is: 19.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.45 : 28.20 = 13.89 : x
  2. Step 2: Convert to fraction form
    20.45/28.20 = 13.89/x
  3. Step 3: Cross multiply
    20.45x = 28.20 × 13.89
  4. Step 4: Simplify right side
    20.45x = 391.70
  5. Step 5: Solve for x
    x = 391.70/20.45
  6. Step 6: Final answer
    x = 19.16

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.