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Finding the Fourth Proportional to 81.07, 121.61 and 20.21

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Solution

The fourth proportional to 81.07, 121.61 and 20.21 is: 30.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.07 : 121.61 = 20.21 : x
  2. Step 2: Convert to fraction form
    81.07/121.61 = 20.21/x
  3. Step 3: Cross multiply
    81.07x = 121.61 × 20.21
  4. Step 4: Simplify right side
    81.07x = 2,457.03
  5. Step 5: Solve for x
    x = 2,457.03/81.07
  6. Step 6: Final answer
    x = 30.31

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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.