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Finding the Fourth Proportional to 20.85, 31.21 and 20.58

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Solution

The fourth proportional to 20.85, 31.21 and 20.58 is: 30.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.85 : 31.21 = 20.58 : x
  2. Step 2: Convert to fraction form
    20.85/31.21 = 20.58/x
  3. Step 3: Cross multiply
    20.85x = 31.21 × 20.58
  4. Step 4: Simplify right side
    20.85x = 642.25
  5. Step 5: Solve for x
    x = 642.25/20.85
  6. Step 6: Final answer
    x = 30.80

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.