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Finding the Fourth Proportional to 81.80, 122.01 and 72.20

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Solution

The fourth proportional to 81.80, 122.01 and 72.20 is: 107.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.80 : 122.01 = 72.20 : x
  2. Step 2: Convert to fraction form
    81.80/122.01 = 72.20/x
  3. Step 3: Cross multiply
    81.80x = 122.01 × 72.20
  4. Step 4: Simplify right side
    81.80x = 8,809.12
  5. Step 5: Solve for x
    x = 8,809.12/81.80
  6. Step 6: Final answer
    x = 107.69

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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.