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Finding the Fourth Proportional to 20.80, 31.09 and 20.60

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Solution

The fourth proportional to 20.80, 31.09 and 20.60 is: 30.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.80 : 31.09 = 20.60 : x
  2. Step 2: Convert to fraction form
    20.80/31.09 = 20.60/x
  3. Step 3: Cross multiply
    20.80x = 31.09 × 20.60
  4. Step 4: Simplify right side
    20.80x = 640.45
  5. Step 5: Solve for x
    x = 640.45/20.80
  6. Step 6: Final answer
    x = 30.79

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.