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Finding the Fourth Proportional to 81.92, 122.88 and 21.05

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Solution

The fourth proportional to 81.92, 122.88 and 21.05 is: 31.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.92 : 122.88 = 21.05 : x
  2. Step 2: Convert to fraction form
    81.92/122.88 = 21.05/x
  3. Step 3: Cross multiply
    81.92x = 122.88 × 21.05
  4. Step 4: Simplify right side
    81.92x = 2,587.12
  5. Step 5: Solve for x
    x = 2,587.12/81.92
  6. Step 6: Final answer
    x = 31.58

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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.