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Finding the Fourth Proportional to 20.80, 28.72 and 13.89

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Solution

The fourth proportional to 20.80, 28.72 and 13.89 is: 19.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.80 : 28.72 = 13.89 : x
  2. Step 2: Convert to fraction form
    20.80/28.72 = 13.89/x
  3. Step 3: Cross multiply
    20.80x = 28.72 × 13.89
  4. Step 4: Simplify right side
    20.80x = 399.05
  5. Step 5: Solve for x
    x = 399.05/20.80
  6. Step 6: Final answer
    x = 19.18

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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.