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Finding the Fourth Proportional to 20.39, 28.10 and 15.21

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Solution

The fourth proportional to 20.39, 28.10 and 15.21 is: 20.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.39 : 28.10 = 15.21 : x
  2. Step 2: Convert to fraction form
    20.39/28.10 = 15.21/x
  3. Step 3: Cross multiply
    20.39x = 28.10 × 15.21
  4. Step 4: Simplify right side
    20.39x = 427.28
  5. Step 5: Solve for x
    x = 427.28/20.39
  6. Step 6: Final answer
    x = 20.95

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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.