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Finding the Fourth Proportional to 20.40, 28.15 and 15.55

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Solution

The fourth proportional to 20.40, 28.15 and 15.55 is: 21.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.40 : 28.15 = 15.55 : x
  2. Step 2: Convert to fraction form
    20.40/28.15 = 15.55/x
  3. Step 3: Cross multiply
    20.40x = 28.15 × 15.55
  4. Step 4: Simplify right side
    20.40x = 437.73
  5. Step 5: Solve for x
    x = 437.73/20.40
  6. Step 6: Final answer
    x = 21.46

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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.