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Finding the Fourth Proportional to 21.85, 30.15 and 20.65

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Solution

The fourth proportional to 21.85, 30.15 and 20.65 is: 28.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.85 : 30.15 = 20.65 : x
  2. Step 2: Convert to fraction form
    21.85/30.15 = 20.65/x
  3. Step 3: Cross multiply
    21.85x = 30.15 × 20.65
  4. Step 4: Simplify right side
    21.85x = 622.60
  5. Step 5: Solve for x
    x = 622.60/21.85
  6. Step 6: Final answer
    x = 28.49

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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.