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Finding the Fourth Proportional to 20.85, 31.30 and 20.47

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Solution

The fourth proportional to 20.85, 31.30 and 20.47 is: 30.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.85 : 31.30 = 20.47 : x
  2. Step 2: Convert to fraction form
    20.85/31.30 = 20.47/x
  3. Step 3: Cross multiply
    20.85x = 31.30 × 20.47
  4. Step 4: Simplify right side
    20.85x = 640.71
  5. Step 5: Solve for x
    x = 640.71/20.85
  6. Step 6: Final answer
    x = 30.73

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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.