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Finding the Fourth Proportional to 21.90, 30.30 and 20.55

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Solution

The fourth proportional to 21.90, 30.30 and 20.55 is: 28.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.90 : 30.30 = 20.55 : x
  2. Step 2: Convert to fraction form
    21.90/30.30 = 20.55/x
  3. Step 3: Cross multiply
    21.90x = 30.30 × 20.55
  4. Step 4: Simplify right side
    21.90x = 622.67
  5. Step 5: Solve for x
    x = 622.67/21.90
  6. Step 6: Final answer
    x = 28.43

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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.