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Finding the Fourth Proportional to 81.32, 121.98 and 20.45

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Solution

The fourth proportional to 81.32, 121.98 and 20.45 is: 30.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.32 : 121.98 = 20.45 : x
  2. Step 2: Convert to fraction form
    81.32/121.98 = 20.45/x
  3. Step 3: Cross multiply
    81.32x = 121.98 × 20.45
  4. Step 4: Simplify right side
    81.32x = 2,494.80
  5. Step 5: Solve for x
    x = 2,494.80/81.32
  6. Step 6: Final answer
    x = 30.68

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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.